Remove custom locking implementation in favor of QLockFile.

Change-Id: Ia55e23c8522050515426ba22fc802bd1878f9d6e
Reviewed-by: Valerio Valerio <valerio.valerio@jollamobile.com>
Remove unused ProcessReadLock class.

Only touched in tests.

Change-Id: I62b31debbbd28206ca22c51385a33e82c2617f64
Reviewed-by: Valerio Valerio <valerio.valerio@jollamobile.com>