CLOUDSTACK-1116 [EC2 Query API] Support for ModifyImageAttribute and ResetImageAttribute

https://reviews.apache.org/r/9213

Add support for EC2 ApiI's ModifyImageAttribute and ResetImageAttribute.
Attributes supported are Description and LaunchPermission.
CLOUDSTACK-1117 [EC2 Query API] DescribeImageAttribute fails

EC2DescribeImageAttribute fails with 'Unsupported - only description supported' error. And this is observed for both the supported attributes 'Description' and 'LaunchPermission'
[EC2 Query API] DescribeAvailabilityZones doesn't have any filter support.

CLOUDSTACK-1118

Support will be available for filters - zone-name and message