caucase.test: Fix test execution outside of a git working copy.

Traversal to the root makes is unreasonable.
Rely on "shell" directory being a sibling of test.py's container.

caucase/test.py

@@ -3839,13 +3839,10 @@ if getattr(CaucaseTest, 'assertItemsEqual', None) is None: # pragma: no cover
   CaucaseTest.assertItemsEqual = CaucaseTest.assertCountEqual
 # pylint: enable=no-member
 
-_caucase_root = os.path.dirname(__file__)
-while not os.path.exists(os.path.join(_caucase_root, '.git')):
-  _caucase_root = os.path.normpath(os.path.join(_caucase_root, os.path.pardir))
 _caucase_sh_path = find_executable(
   'caucase.sh',
   path=os.path.join(
-    _caucase_root, 'shell',
+    os.path.dirname(__file__), os.path.pardir, 'shell',
   ) + os.path.pathsep + os.getenv('PATH', ''),
 )
 def _runCaucaseSh(*args):