gclient: Sync CIPD deps before running hooks.

Bug: 882611
Change-Id: I72646544a164f557ea7d53e0ce0f16d663618a98
Reviewed-on: https://chromium-review.googlesource.com/c/1255446Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

testing_support/fake_repos.py

@@ -756,7 +756,12 @@ deps = {
     ],
     'dep_type': 'cipd',
   },
-}""",
+}
+hooks = [{
+  # make sure src/repo12 exists and is a CIPD dir.
+  'action': ['python', '-c', 'with open("src/repo12/_cipd"): pass'],
+}]
+""",
       'origin': 'git/repo_13@3\n'
     })