core: Remove GetStorageServerConnectionsQuery

GetStorageServerConnectionsQuery is not used anywhere in the code, and
hence should be removed.

This patch removes the following:
1. The GetStorageServerConnectionsQuery class
2. The GetStorageServerConnections constant representing it in
   VdcQueryType
3. The getAll() method in StorageServerConnectionsDAO (which was only
   used by the query), its implementation, and its test.
4. The GetAllFromstoage_server_connections stored procedure that was
   only used by the said DAO function.

Note that the test for StorageServerConnectionsDao.get(Guid) is slightly
redone so it no longer depends on getAll()'s implementation.

Change-Id: I352f819dd3a7b272ccf1b39cfcf76cca62a8ee10
Signed-off-by: Allon Mureinik <amureini@redhat.com>