Fix wrong create/update/delete flags for vmstorages

For vmstorages now, we always use 'CURRENT' flag,
this will result in change not take effective when vm's reboot.
Now use get_vm_config_flag probe the current status of vm,
and change according to vm status.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Adding test case for updating flags

Add test case for flags change to make sure it works
after vm powered off.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Change doc and controllor to support cdrom eject

Add eject action to vmstorage actions,
and add this action to doc.
Instead of reuse 'update', make eject a single action to avoid empty
path introduced confusion.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Update model to support cdrom eject

Modify xml generation to adjust to cdrom eject change.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Add testcase for cdrom eject

Add cdrom eject testcase to make sure it works properly.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>