webadmin: refactor volume list action availability

Refactored update available actions code which depends
on volume selections. Introduced individual boolean flags
for deciding the availability of the actions
to avoid multiple calls to the actual command availablity methods.

Change-Id: I7f003dfe536189e1fa1d38e380e7acb7db208a22
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>