Fix its-rtc creating a fresh facade for each request

So far, a new RTCFacade was created every time a request was done. That
led to the creation of unnecessary objects and to the log being flooded
with connection messages.

Bind RTCFacade as a singleton and change the log level back to INFO.

Bug: Issue 3575
Change-Id: I5e7e717915d7fc09b2926b21ff706a6a31b41710