file-posix: Use error API properly

file-posix: Use error API properly

Use error_report for situations that affect user operation (i.e.  we're
actually returning error), and warn_report/warn_report_err when some
less critical error happened but the user operation can still carry on.

For raw_normalize_devicepath, add Error parameter to propagate to
its callers.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>