This change updates etherpad to version 1.9.7 from 1.9.6. The
changelog [0] is minimal, but does indicate there are changes to plugin
installations. Looking at the upstream Dockerfile, which we based our
Dockerfile on, there are no changes between 1.9.6 and 1.9.7 implying
this plugin installation update is transparent to us. That said we
should hold a node and test that our plugins are working as expected.
[0] https://github.com/ether/etherpad-lite/blob/v1.9.7/CHANGELOG.md
Change-Id: Ie708299fae39549f048f37938daa60668189be67
a53dcc8a7d