Description of problem: 'IPATrustPackageCheck' should display msg when ipa-server-trust-ad package is not installed

Version-Release number of selected component (if applicable):
[root@master ~]# cat /etc/redhat-release
Red Hat Enterprise Linux release 8.2 Beta (Ootpa)
ipa-healthcheck-0.3-4.module+el8.1.0+4098+f286395e.noarch

How reproducible: Always

Steps to Reproduce:
1. Install ipa-healthcheck
2. Run the below command with ipa-server-trust-ad not installed on the system.

#ipa-healthcheck --source ipahealthcheck.ipa.trust

Actual results:

{
"source": "ipahealthcheck.ipa.trust",
"check": "IPATrustPackageCheck",
"result": "SUCCESS",
"uuid": "e7007c10-9cc3-43d8-bfa9-e45c697ea9ea",
"when": "20191118134632Z",
"duration": "0.000019",
"kw": {}
}

Expected results: We could display in "msg" that "ipa-server-trust-ad"
package is not installed if its actually not present.

"kw": {
"msg": "ipa-server-trust-ad package is not installed",

Additional info: