core: allow identical path for different local domains

StorageServerConnectionCommandBase -> isConnWithSameDetailsExists:
Added a specific validation for local domains connections;
allowing identical path for local domains residing
on different data-centers.

Note: as a future work, we should add a unique identification
for a local domains connections (e.g. to differentiate between
local connections retrieved from the rest-api).

Change-Id: I4628d7fa442b959d5582e44386f31518b98852e7
Bug-Url: https://bugzilla.redhat.com/1023739
Signed-off-by: Daniel Erez <derez@redhat.com>