Don't "hang" gclient if fast-forward is not possible.

As noticed in the TODO, raw_input (used by ask_for_data) works badly
on background threads. On my Windows it doesn't even print the prompt which
makes it hard to interact with it.

Better to just abort and tell the user of gclient how to proceed.

BUG=

Review URL: https://chromiumcodereview.appspot.com/15421005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@201295 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/tests/gclient_scm_test.py b/tests/gclient_scm_test.py
index 3f1ff3b..babd133 100755
--- a/tests/gclient_scm_test.py
+++ b/tests/gclient_scm_test.py
@@ -684,6 +684,7 @@
       self.reset = False
       self.nohooks = False
       self.merge = False
+      self.jobs = 1
       self.delete_unversioned_trees = False
 
   sample_git_import = """blob