Initial support for Fedora 21

Initial support for Fedora 21.  Add f21 to the distribution lists for
rpms, ensure "mariadb" is used over "mysqld" and enable it in the
distro check, as we have several reports of it working.

Tested with [1]

[1] http://download.fedoraproject.org/pub/fedora/linux/releases/test/21-Beta/Cloud/Images/x86_64/Fedora-Cloud-Base-20141029-21_Beta.x86_64.qcow2

Change-Id: I97cbede806e5c00363c7174fa1e9f286de96aab6
diff --git a/files/rpms/swift b/files/rpms/swift
index 9ec4aab..ccda22b 100644
--- a/files/rpms/swift
+++ b/files/rpms/swift
@@ -6,7 +6,7 @@
 python-greenlet
 python-netifaces
 python-nose
-python-paste-deploy # dist:f19,f20,rhel7
+python-paste-deploy # dist:f19,f20,f21,rhel7
 python-simplejson
 python-webob
 pyxattr