Adds tests, fixes Radware LBaaS driver as a result

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