Fix failed attempt at configuration defaults

The default needs to be changed later. Oops.

Change-Id: Ibcdc646a1e961a428f500d3d57b39c0a905880d2
(cherry picked from commit afb1310c6526370cd3ca9b4b654770f4e2dfbe48)
Use MakeGlobalVariablesScript to set wgMediaViewerOnClick

Use MakeGlobalVariablesScript instead of ResourceLoaderGetConfigVars
to set wgMediaViewerOnClick because the first is cached per-site
and we need per-user caching.

Change-Id: Ib4d99698030b69532b5996fa6b981f2b5c556a23
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/263
(cherry picked from commit 23dc9423340f6285465917874b10b433903673f4)
Merge "Fix failed attempt at configuration defaults" into wmf/1.23wmf20
Merge "Use MakeGlobalVariablesScript to set wgMediaViewerOnClick" into wmf/1.23wmf20