Add InvalidExternalNetwork exception to display correct error

Fixes bug 1075089

The message in the BadRequest exception raised in file
quantum/tests/unit/test_l3_plugin.py is
being muted in the logfile  since the BadRequest is
catched and writes its own log message.

Change-Id: Ia0140620205a80dd4b3637b2d41562adb7992b5c
Add execute file mode bits to quantum-mlnx-agent

chmod a+x bin/quantum-mlnx-agent

Change-Id: I363e4e1ab43925964b5da866ec8843317c43dbcb
Merge "Add InvalidExternalNetwork exception to display correct error"
Merge "Add execute file mode bits to quantum-mlnx-agent"