Normalize args when deriving the redis lock key.

[dylanahsmith]

Otherwise, the before_enqueue_lock will create a different redis key than around_perform_lock deletes.

This can be tested by using a symbol in the arguments, which gets encoded as a string. A regression test was added to unsure this issue is handled.

[orlando]

+1, i came across this today

[joshfrench]

+1, locks with symbolized arguments are never deleted from Redis.

[rockrep]

+1