When rule does not specify forced target (`target=...`), generic
`$dispvm` wasn't resolved to specific Disposable VM (based on
`default_dispvm` property).
This socket (and commands) are not exposed to untrusted input, so no
need to extensive sanitization. Also, there is no need to provide a
stable API here, as those methods are used internally only.
QubesOS/qubes-issues#853
This is rewritten version of core-admin-linux/qrexec/qrexec-policy.
It's placed outside of `qubes` module on purpose - to avoid imporing it,
which require a lot of time.
QubesOS/qubes-issues#865QubesOS/qubes-issues#910
