Bug 1169089 - Detect CentOS 7 in bootstrapper; r=gps

CentOS has apparently changed its disto name. Detect the new version.

DONTBUILD (NPOTB)

--HG--
extra : commitid : JrYp4WJ5Fs3
extra : amend_source : c2ac16f7006c2e44450de54edb732fa722f150d0

python/mozboot/mozboot/bootstrap.py

@@ -64,7 +64,7 @@ class Bootstrapper(object):
         if sys.platform.startswith('linux'):
             distro, version, dist_id = platform.linux_distribution()
 
-            if distro == 'CentOS':
+            if distro in ('CentOS', 'CentOS Linux'):
                 cls = CentOSBootstrapper
             elif distro in ('Debian', 'debian'):
                 cls = DebianBootstrapper