Removes test_force_delete_server_invalid_state negative test

Commit I06a476701ccb47d8f7fd6e43c394ccb3fac2b3aa allows the force
deleting of running instances as well as those in soft-delete state
so this negative test is no longer appropriate.

Related-Bug: #1351001
Change-Id: Ia6d09fea753196a8bc9f33ac8acaae49f1d306e7
Merge "Removes test_force_delete_server_invalid_state negative test"