ipatests: add tests for ipa host-add with non-default maxhostnamelength
Implement test for ticket 2018: Change hostname length limit to 64.
The fix provides a new configuration parameter (maxhostname) that can be modified through ipa config-mod, and governs the max hostname len allowed through ipa host-add.
Add new tests:
- check that maxhostname cannot be changed to a value < 64
- check that ipa host-add is refused if the hostname length is > maxhostname
- check that ipa host-add is OK if the hostname length is <= maxhostname
Related: https://pagure.io/freeipa/issue/2018