Adds tests, fixes Radware LBaaS driver as a result

Adding more tests for Radware LBaaS driver.
Adding new exception module for the Radware lbaas driver.
The base radware lbaas exception, called RadwareLBaasException,
Several specific exceptions for different failures.
Driver was changed for using new exceptions as well.
Changing the way OperationsHandler obtains context.
Always waiting 1 second before handling the operation
next time, to prevent busy-wait requests on vDirect.
Several code optimizations were done as well.

Change-Id: I15f7845fc2575eedb62c47d15ee6c1cea08e22f5
Closes-Bug: #1236741
Add request-id to log messages

request-id needs to be stored in thread local store to allow
openstack.common.log use request-id.
tenant_name and user_name are added to the context so that
they can be logged by customizing the log format.

Also replaces 'cxt' with 'ctx' in test_neutron_context.py.
Previously both 'ctx' and 'cxt' are used mixed in one file.

Change-Id: Ib921585e648e92491c1366bc0ad26a6ae71e2fc9
Partial-Bug: #1239923
Merge "Add request-id to log messages"
Merge "Adds tests, fixes Radware LBaaS driver as a result"