engine: Removing validateStorageServerConnection - storage part

The following patch is removing uses of validateStorageServerConnection.
The API is depricated and usefull, espicially when it called from canDoaction of internal commands
Benefit, reduced XML RPC call at most of the storage operations, reduced useless logic

Change-Id: I7b3bc2491943a6daa21228e37169c83f32865984
Signed-off-by: Michael Kublin <mkublin@redhat.com>