git_cache: remove redundant code.

R=iannucci@chromium.org, nodir@chromium.org

Change-Id: If7d48775b01a55e884a4c1fd6c26b1ff65992f4e
Reviewed-on: https://chromium-review.googlesource.com/786823
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>

git_cache.py

@@ -509,7 +509,7 @@ class Mirror(object):
       self.print(GIT_CACHE_CORRUPT_MESSAGE)
       tempdir = self._ensure_bootstrapped(depth, bootstrap, force=True)
       assert tempdir
-      self._fetch(tempdir or self.mirror_path, verbose, depth)
+      self._fetch(tempdir, verbose, depth)
     finally:
       if tempdir:
         if os.path.exists(self.mirror_path):