Fix qubes.xml unlock code (#748)
Fix qubes.xml unlock code (#748)

Do not call explicit lockf(lOCK_UN) to not unlock the file
buffers are flushed. This is simpler than adding flush() call.

woju/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin