Move mac_bsdextended check up before running the test_libugidfw_strings testcases

I realize that these tests could be run before mac_bsdextended is loaded, but
it would overcomplicate things to special case handle the testcases before doing
the mac_bsdextended(4) feature check

The testcases will be split up so they can be run separately in the near future

MFC after: 3 days
Sponsored by: EMC / Isilon Storage Division