RPC Final migration to DQMEDAnalyzer

Changed the last remaining source modules (step 1) to inherit from DQMEDAnalyzer in the RPC DQM code.
@acimmino could you please move this scope to the dqmBeginRun method as described in:
https://twiki.cern.ch/twiki/bin/viewauth/CMS/ThreadedDQM#The_DQMEDAnalyzer
?