[autotest] ignore milestones when looking at factory/firmware branches

In the suite scheduler, we intend to ignore the numeric milestones
when deciding to run a suite on a factory/firmware build.  The code
was not doing this.  Now it is.

BUG=chromium-os:31415
TEST=unit

Change-Id: I14d989980066ffaa57184b45ef2bace3057c7c08
Reviewed-on: https://gerrit.chromium.org/gerrit/24120
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Chris Masone <cmasone@chromium.org>
Commit-Ready: Chris Masone <cmasone@chromium.org>
diff --git a/site_utils/suite_scheduler/task.py b/site_utils/suite_scheduler/task.py
index 4dbc383..1290b49 100644
--- a/site_utils/suite_scheduler/task.py
+++ b/site_utils/suite_scheduler/task.py
@@ -132,7 +132,6 @@
                         spec.lstrip('>=R'))
                 else:
                     self._bare_branches.append(spec)
-
         # Since we expect __hash__() and other comparitor methods to be used
         # frequently by set operations, and they use str() a lot, pre-compute
         # the string representation of this object.
@@ -150,9 +149,10 @@
         @param branch: the branch to check.
         @return True if b 'fits' with stored specs, False otherwise.
         """
-        return (branch in self._bare_branches or
-                (self._numeric_constraint and
-                 version.LooseVersion(branch) >= self._numeric_constraint))
+        if branch in BARE_BRANCHES:
+            return branch in self._bare_branches
+        return (self._numeric_constraint and
+                version.LooseVersion(branch) >= self._numeric_constraint)
 
 
     @property