heat tests : remove duplicate import

Change-Id: I20364f10041420d898e3255adcc12f3a8f53ed03
Signed-off-by: Steven Hardy <shardy@redhat.com>
heat tests : fix StackControllerTest name duplication

StackControllerTest appears twice in the run_tests.sh output,
since it's used for both the CFN and ReST API tests, so rename
the CFN testcase to make run_tests output less confusing

Change-Id: Iedf2e21ecd0b511eb93a11c2cf593dbfc1bcaca9
Signed-off-by: Steven Hardy <shardy@redhat.com>