OPENDJ-2522 rpm: error message in logs when uninstalling after an upgrade

The LockFileManager relies on lock files for locking.
Problem is that in this issue, the file paths computed during server startup
are not the same computed as the ones during server shutdown.

During startup, the Strings put into sharedLocks and sharedLockReferences are of the folowing form:
    "/opt/opendj/./locks/backend-monitor.lock"
While on shutdown they have the following form:
    "/opt/opendj/locks/backend-monitor.lock"
Since the strings do not equal, this message is shown.
This is worrying since it seems any lock checks will be wrong too. :(

The solution is to change Utils.getInstancePathFromInstallPath() to return a canonical path (instead of absolute)