plugins: Delete noisy and useless debug message (#4409)
plugins: Delete noisy and useless debug message (#4409)

The debug statement mostly printed the following useless message over
and over, causing Travis CI logs to become truncated:

    [DEBUG] pluginfw - [ undefined ] returning
storytouch/etherpad-lite,ether/etherpad-lite,ether/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite