Volume xml client translate json attribute names

Translate the XML special attribute names
 to the same as we get via the json api.

Also changing the _check_if_bootable will be called only from the
_parse_volume.

Change-Id: I32ba5001a84bbee9459b3c9ce7a70d48fede22bd
Fix test case in security groups

In test_server_security_groups test case, the return
value of delete_security_group is not properly validated

Change-Id: Ib967dda50898bdcadb2d02398429d2f7edd10121
Closes-Bug: #1318636
Merge "Volume xml client translate json attribute names"
Merge "Fix test case in security groups"