Fix plugin not loading because of duplicated binding

Loading the plugin failed with a Guice exception [1] given that the same
binding was already defined by its-base and it was being loaded when
invoking the its-base module from its-rtc.

Remove duplicate binding from its-rtc.

[1] http://pastebin.com/a4JtTdZe

Change-Id: Ib4b9fac935f6e8ca1d7d75e1a990206958c6f096