Split the timed mutex lock from the non-timed lock functions

Split the timed mutex lock from the non-timed lock functions

Non-timed mutex locks are by far more common, so let's try not to
penalise the locking of those with code that won't get used that
often.

Change-Id: I37f56d6429836467fdec2e588c0fb22d914b5d75
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>