Description of problem:
From RHEL 7 most DS plugins are converted to be betxn - if their operation fails, whole transaction should fail and not be comitted to database. In case of Linked Attributes plugin, we can create a situation where plugin fails to create linked attribute in managed entry, e.g. due to non-existent managed entry.

Version-Release number of selected component (if applicable):
389-ds-base-1.3.1.6-8.el7.x86_64

How reproducible:
always

Steps to Reproduce:

# Enable plugin
[jrusnack@localhost slapd-dstet]$ ldapmodify -h $HOST -p $PORT -D "cn=directory manager" -w Secret123 -a <<EOF
> dn: cn=Linked Attributes,cn=plugins,cn=config
> changetype: modify
> replace: nsslapd-pluginEnabled
> nsslapd-pluginEnabled: on
> EOF
modifying entry "cn=Linked Attributes,cn=plugins,cn=config"

# Set up new linked attribute seeAlso
[jrusnack@localhost slapd-dstet]$ ldapmodify -h $HOST -p $PORT -D "cn=directory manager" -w Secret123 -a <<EOF
> dn: cn=Manager Link,cn=Linked Attributes,cn=plugins,cn=config
> changetype: add
> objectClass: top
> objectClass: extensibleObject
> cn: Manager Link
> linkType: seeAlso
> managedType: seeAlso
> EOF
adding new entry "cn=Manager Link,cn=Linked Attributes,cn=plugins,cn=config"

# Restart DS to apply changes
[jrusnack@localhost slapd-dstet]$ sudo systemctl restart dirsrv.target

# Add manager entry, which links to non-existent uid=user
[jrusnack@localhost slapd-dstet]$ ldapmodify -h $HOST -p $PORT -D "cn=directory manager" -w Secret123 -a <<EOF
> dn: uid=manager,ou=people,dc=example,dc=com
> objectclass: person
> objectclass: inetOrgPerson
> objectclass: top
> cn: manager
> sn: manager
> uid: manager
> seeAlso: uid=user,ou=people,dc=example,dc=com
> EOF
adding new entry "uid=manager,ou=people,dc=example,dc=com"

[jrusnack@localhost slapd-dstet]$ ldapsearch -h $HOST -p $PORT -D "cn=directory manager" -w Secret123 -b "uid=manager,ou=people,dc=example,dc=com" -LLL
dn: uid=manager,ou=People,dc=example,dc=com
objectClass: person
objectClass: inetOrgPerson
objectClass: top
objectClass: organizationalPerson
cn: manager
sn: manager
uid: manager
seeAlso: uid=user,ou=people,dc=example,dc=com
[jrusnack@localhost slapd-dstet]$ ldapsearch -h $HOST -p $PORT -D "cn=directory manager" -w Secret123 -b "uid=user,ou=people,dc=example,dc=com" -LLL
No such object (32)
Matched DN: ou=people,dc=example,dc=com


Actual results:
Manager entry is created even though creating linked attribute in entry uid=user failed (uid=user does not exist).