add test same host in different files in dir

tests issue #5749
 same host defined in different groups which in turn are defined
 in different ini files in an inventory directory

Conflicts:
	test/units/TestInventory.py
modifed test to use get_hosts instead of get_groups

closes #5749

Conflicts:
	test/units/TestInventory.py
Formatting cleanup.

Post merging of GH-5837 via GH-5749.