Add helper for declaring all locks shared

This patch adds a function for abstracting
“dict.fromkeys(locking.LEVELS, 1)”. It also removes a duplicate
assignment for the share_locks in LUInstanceQuerydata.

Additionally, it moves the _SupportsOob function to the helper
function list.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>