Fixed bmv2.py assigning gRPC/Thrift port already in use
Fixed bmv2.py assigning gRPC/Thrift port already in use

Also handle Mininet exceptions by shutting down all BMv2 instances

Change-Id: I5a8d1a06441daa57c5dd3b0861f1b7484828174a

opennetworkinglab/onos,opennetworkinglab/onos,kuujo/onos,gkatsikas/onos,kuujo/onos,kuujo/onos,gkatsikas/onos,opennetworkinglab/onos,oplinkoms/onos,oplinkoms/onos,opennetworkinglab/onos,oplinkoms/onos,oplinkoms/onos,kuujo/onos,opennetworkinglab/onos,oplinkoms/onos,oplinkoms/onos,kuujo/onos,kuujo/onos,oplinkoms/onos,gkatsikas/onos,gkatsikas/onos,kuujo/onos,gkatsikas/onos,gkatsikas/onos,opennetworkinglab/onos