Install redis 2.10.3

This seems to be the only version that works; and is the version on
the current ask.o.o server.  Ensure it doesn't upgrade to something
later.

Change-Id: I32a887b014aed376c61ce9f5dcf14668c2d357ce

manifests/install.pp

@@ -121,6 +121,16 @@ class askbot::install (
     require    => Python::Virtualenv['/usr/askbot-env'],
   }
 
+  # This seems to be the only version that works; after this start
+  # getting errors about CacheKey input types; you can search and find
+  # this is something to do with redis 3.
+  python::pip { 'redis':
+    ensure     => '2.10.3',
+    pkgname    => 'redis',
+    virtualenv => '/usr/askbot-env',
+    require    => Python::Virtualenv['/usr/askbot-env'],
+  }
+
   include ::httpd::mod::wsgi
 
   exec { 'askbot-install':