Adds negative test to test_instance_controller.py

This submission adds a new negative unittest
"test_validate_create_invalid_name" under
"trove/tests/unittests/instance" script, to validate
instance creation with invalid name.

Change-Id: I4611c136e611214f901eb35fbbb613ab1107a4df
Merge "Adds negative test to test_instance_controller.py"