Description of problem:
DS shuts down automatically if dnaThreshold is set to 0 in a MMR setup

Version-Release number of selected component (if applicable):
[root@ds ~]# rpm -qa | grep 389
389-ds-base-libs-1.3.5.10-1.el7.x86_64
389-ds-base-1.3.5.10-1.el7.x86_64

How reproducible:
Always

Steps to Reproduce:
It's a MMR setup with 2 masters
 
1. Enabled the dna plugin on both instances
 
2. Added the required container entries for the dna plugin on both masters
 
3. Now on master1 which will basically transfer the next range to master2, I added the dna plugin configuration entry like this:
dn: cn=Account UIDs,cn=Distributed Numeric Assignment Plugin,cn=plugins,cn=config
objectClass: top
objectClass: dnaPluginConfig
cn: Account UIDs
dnatype: uidNumber
dnatype: gidNumber
dnafilter: (objectclass=posixAccount)
dnascope: ou=People,dc=example,dc=com
dnaNextValue: 1
dnaMaxValue: 50
dnasharedcfgdn: cn=Account UIDs,ou=Ranges,dc=example,dc=com
dnaThreshold: 0
dnaRangeRequestTimeout: 60
dnaMagicRegen: magic
dnaRemoteBindDN: uid=dnaAdmin,ou=People,dc=example,dc=com
dnaRemoteBindCred: secret123
dnaNextRange: 80-90
 
As can be seen in the above entry, I've set dnaThreshold to '0' and the dnaNextRange to 80-90
 
4. Then on master2, I added dna plugin configuration entry like this,
dn: cn=Account UIDs,cn=Distributed Numeric Assignment Plugin,cn=plugins,cn=config
objectClass: top
objectClass: dnaPluginConfig
cn: Account UIDs
dnatype: uidNumber
dnatype: gidNumber
dnafilter: (objectclass=posixAccount)
dnascope: ou=People,dc=example,dc=com
dnanextvalue: 61
dnaMaxValue: 70
dnasharedcfgdn: cn=Account UIDs,ou=Ranges,dc=example,dc=com
dnaThreshold: 2
dnaRangeRequestTimeout: 60
dnaMagicRegen: magic
dnaRemoteBindDN: uid=dnaAdmin,ou=People,dc=example,dc=com
dnaRemoteBindCred: secret123
 
master2 only has 10 numbers which it can allocate automatically for uidNumber and gidNumber attributes
 
5. Then I added added the required replication configuration entries on both masters to configure replication
 
6. Added 10 entries on master2 to exhaust its available range
 
7. Did an ldapsearch on master2, all the 10 entries were added and the attributes uidNumber and gidNumber were
set accordingly by dna plugin, so far so good
 
8. Now I tried adding 11th entry on master2, It basically failed with this error
ldap_add: Operations error (1)
additional info: Allocation of a new value for range cn=account uids,cn=distributed numeric assignment plugin,cn=plugins,cn=config failed! Unable to proceed.
 
9. Checked the error logs on master2, this is what they show
[01/Jul/2016:18:11:00.370146064 +051800] slapi_ldap_bind - Error: could not send bind request for id [uid=dnaAdmin,ou=People,dc=example,dc=com] authentication mechanism [SIMPLE]: error -1 (Can't contact LDAP server), system error -5987 (Invalid function argument.), network error 107 (Transport endpoint is not connected, host "ds.example.com:3389")
[01/Jul/2016:18:12:49.411378922 +051800] dna-plugin - dna_request_range: Error sending range extension extended operation request to server ds.example.com:3389 [error -1]
[01/Jul/2016:18:12:49.536799341 +051800] dna-plugin - dna_pre_op: no more values available!!
[01/Jul/2016:18:14:12.466096468 +051800] slapi_ldap_bind - Error: could not send bind request for id [uid=dnaAdmin,ou=People,dc=example,dc=com] authentication mechanism [SIMPLE]: error -1 (Can't contact LDAP server), system error -5987 (Invalid function argument.), network error 107 (Transport endpoint is not connected, host "ds.example.com:3389")
 
10. Upon investing with status-dirsrv, I found that master1 was killed
[root@ds ~]# status-dirsrv mast1
● dirsrv - 389 Directory Server mast1.
   Loaded: loaded (/usr/lib/systemd/system/dirsrv@.service; enabled; vendor preset: disabled)
   Active: failed (Result: signal) since Thu 2016-07-07 20:35:23 IST; 9min ago
 Main PID: 5852 (code=killed, signal=FPE)
   Status: "slapd started: Ready to process requests"
 
The status however here still shows Ready to process requests
 
11. Restarted master1 with start-dirsrv master1
 
12. Checked error logs on master1, this is what they show
[01/Jul/2016:18:18:04.629383441 +051800] Detected Disorderly Shutdown last time Directory Server was running, recovering database.
[01/Jul/2016:18:18:04.816326545 +051800] NSMMReplicationPlugin - changelog program - _cl5NewDBFile: PR_DeleteSemaphore: /var/lib/dirsrv/slapd-mast1/changelogdb/62f98283-3f8811e6-8e9ac15d-c133e87f.sema; NSPR error - -5943
[01/Jul/2016:18:18:04.974329732 +051800] NSMMReplicationPlugin - replica_check_for_data_reload: Warning: disordely shutdown for replica dc=example,dc=com. Check if DB RUV needs to be updated
[01/Jul/2016:18:18:05.011287516 +051800] slapd started.  Listening on All Interfaces port 3389 for LDAP requests
 
13. Did an ldapsearch on master1 and found that only some of the 10 entries that were added on master2 were replicated to master1 and others were missing