Description of problem:
[reproduced on RHEL 7.6 / ipa-4-6 so far]

* install IDM
* configure AD trust
* add a trust to an AD forest
* search for trust objects in AD LDAP: they should be there
* uninstall the last IDM master
* check whether AD LDAP still has the trust objects


Version-Release number of selected component (if applicable):
ipa-server-4.6.4-10.el7.x86_64
ipa-server-trust-ad-4.6.4-10.el7.x86_64


How reproducible:
Always on RHEL 7.6 at least


Steps to Reproduce:
0. Have an AD Forest ready and create a forest trust from IDM: 
1. ipa-server-install
2. ipa-adtrust-install --add-sids  --add-agents -U
3. ipa trust-add --type=ad '<domain>' --admin '<AD admin>' --password --range-type=ipa-ad-trust
4. ipa-server-install --uninstall -U
5. Search for trust objects in AD LDAP:
- ldapsearch -x -h dc1.adexample.com  -D "administrator"  -W -b "dc=adexample,dc=com" '(flatname=IDM)' flatname
- ldapsearch -x -h dc1.adexample.com -D "administrator"  -W -b "dc=adexample,dc=com" '(samaccountname=IDM*)' samaccountname userAccountControl

Actual results:
$ ldapsearch -x -h dc1.adexample.com  -D "administrator"  -W -b "dc=adexample,dc=com" '(flatname=IDM)' flatname

# idm.adexample.com, System, adexample.com
dn: CN=idm.adexample.com,CN=System,DC=adexample,DC=com
flatName: IDM

$ ldapsearch -x -h dc1.adexample.com -D "administrator"  -W -b "dc=adexample,dc=com" '(samaccountname=IDM*)' samaccountname userAccountControl
Enter LDAP Password: 

# IDM$, Users, adexample.com
dn: CN=IDM$,CN=Users,DC=adexample,DC=com
userAccountControl: 2080
sAMAccountName: IDM$


Expected results:
None of the ldapsearches should find anything AD LDAP.
ipa-server-install --uninstall when executed on the last IDM Trust Agent should remove its trust agreements(s) early.