Bug 6176 - Decrease logging level in Sal-F/G/M-Service and use synchronized BiMap

Bug 6176 - Decrease logging level in Sal-F/G/M-Service and use synchronized BiMap

 - decrease logging level to prevent overloading of netty
   thread with logging errors (seen in troughput test)
 - despite the fact that unsuccesful RPCresult brings errors
   from device there is no reason for throwing error since
   it is not error of karaf ot OFP itself (therefore debug)
 - change BiMap to synchronized because of ConcurrentModificationException
   seen in tests

Change-Id: Ia37212647a9c119ecd51d6685ea8fffb8ee94a39
Signed-off-by: Andrej Leitner <andrej.leitner@pantheon.tech>