Turn cobertura quiet mode
Turn cobertura quiet mode

- INFO message to stderr by Cobertura command was incorrectly
  interpreted by Jenkins' Maven log parser as an ERROR.
  Enabled quiet option to suppress INFO message to stderr.

Change-Id: I8ad36283b31e29e87aa207bc5e6fc7aaecd9293c

opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open