This updates etherpad to the current develop branch state
(commit 08f199178d2932cc0ec956aaeb3f62e8a535598a) to pull in a fix after
the v2.2.4 release and before v2.2.5. Specifically we're interested in a
fix for embedding etherpad as we do with meetpad.
If a 2.2.5 release is pushed before this lands we should switch over to
that instead.
Change-Id: I497c6b434dae54ed808f62143a4c12fb42cc2c47
64d3f79fc4