Give up on parallel checkout by default.

gclient.py

Index: gclient.py
diff --git a/gclient.py b/gclient.py
index 9721f426aec23358448f275ab4bb7ce2906a9137..9eec5d8b73b0747098b3cea68e4c4b488a1d8300 100644
--- a/gclient.py
+++ b/gclient.py
@@ -1175,15 +1175,7 @@ def Main(argv):
         '  %-10s %s' % (fn[3:], Command(fn[3:]).__doc__.split('\n')[0].strip())
         for fn in dir(sys.modules[__name__]) if fn.startswith('CMD')]))
     parser = optparse.OptionParser(version='%prog ' + __version__)
-    # TODO(maruel): Temporary workaround to disable parallel checkout on
-    # buildbots until they can correctly parse its output. stdout being
-    # redirected is not a good signal, at least on linux. Check for environment
-    # variable instead.
-    if 'CHROME_HEADLESS' not in os.environ:
-      jobs = 8
-    else:
-      jobs = 1
-    parser.add_option('-j', '--jobs', default=jobs, type='int',
+    parser.add_option('-j', '--jobs', default=1, type='int',
                       help='Specify how many SCM commands can run in parallel; '
                            'default=%default')
     parser.add_option('-v', '--verbose', action='count', default=0,