Improve parameter related EC2 error codes

This patch replaces parameter/attribute related raises of EC2APIError
with specific exceptions.

 * Introduce new MissingParameter exception with 'MissingParameter'
   ec2_code.
 * Introduce new InvalidAttribute exception which isn't a valid EC2
   error code but it's needed nonetheless as the nova EC2 API isn't
   fully compatible.
 * Add 'InvalidParameterValue' ec2_code to existing
   InvalidParameterValue exception and use it where appropriate. Also
   add it to existing InvalidPortRange exception.

Implements: blueprint ec2-error-codes

Change-Id: I7820edfd9045fdc817a8538a754c9add20b68cf4
Merge "Improve parameter related EC2 error codes"