Remove runtime's lockDir as it is no longer needed after the lock
rework.
Add a trivial in-memory lock manager for unit testing
Signed-off-by: Matthew Heon <matthew.heon@gmail.com>
Move SHM specific code into a subpackage. Within the main locks
package, move the manager to be linux-only and add a non-Linux
unsupported build file.
Signed-off-by: Matthew Heon <matthew.heon@gmail.com>