This error happens when a plugin is loaded after Gerrit.awaitPluginsLoaded
completes. Gerrit._endpoints.getDetails inits the module and then
Gerrit._endpoints.onNewEndpoint inits the module a second time. This renders
the same endpoint on the screen twice.
Change-Id: I65c7430f6d1350d1287b400a9ea1d6e275f8e8da