Description of problem: Add check and avoid error message displayed while
adding external trust with option --range-type having values
ipa-ad-trust-posix/ipa-ad-trust


Version-Release number of selected component (if applicable):
ipa-server-trust-ad-4.4.0-1.el7.x86_64
ipa-server-4.4.0-1.el7.x86_64

How reproducible:Always


Steps to Reproduce:

1. Add external trust with range-type as ipa-ad-trust-posix

[root@server sssd]# ipa trust-add --type='ad' --base-id=150000
--range-size=10000 --range-type='ipa-ad-trust-posix'
Realm name: test.qa
Active Directory domain administrator: administrator
Active Directory domain administrator's password:

2. Add external trust with range-type as ipa-ad-trust

[root@server sssd]# ipa trust-add --type='ad' --base-id=150000
--range-size=10000 --range-type='ipa-ad-trust'
Realm name: test.qa
Active Directory domain administrator: administrator
Active Directory domain administrator's password:

Actual results:
1. ipa: ERROR: Domain 'test.qa' is not a root domain for forest 'pne.qe'
2. ipa: ERROR: Domain 'test.qa' is not a root domain for forest 'pne.qe'


Expected results:
Add checks and avoid the error.

Additional info: Test enviornment.

pne.qe is forest root domain
test.qa is the tree root domain.