core: supress findbugs warning in StorageServerConnectionCommandBase

after change I0fc70dd4e7988f4ea4597f016c9de8419c17adfa findbugs
complains about null pointer dereference of connections which is wrong.

Change-Id: I139f33ddba33cfb109145505afc1aea609c82807
Signed-off-by: Liron Aravot <laravot@redhat.com>