This patch acts as a base framework to add the parameters needed
for manage volume support.
This includes 2 changes:
1. Move get_parser and take_action code to common methods which
can be utilized by both v2 and v3
2. Make _check_size_arg as a static method and move it inside
CreateVolume class since it's not used by other classes.
[2] was initially thought to be a follow up change but since we
are implementing changes into the _check_size_arg method for v3,
it makes sense to just include it in CreateVolume class to avoid
adding a new additional method. Similar changes are done for v2
as well.
Change-Id: I9315e457ebd6c5ba4cc67452f92c9dc8c139ee3c
0d9ace6425