Add option to uniformly start new DispVM from either VM or Dom0. This
use DispVMWrapper, which translate it to either qrexec call to $dispvm,
or (in dom0) to appropriate Admin API call to create fresh DispVM
first.
This require abandoning registering --all and --exclude by
QubesArgumentParser, because we need to add --dispvm mutually exclusive
with those two. But actually handling those two options is still done by
QubesArgumentParser.
This also updates man page and tests.
FixesQubesOS/qubes-issues#2974
since qvm-run use multiprocessing.Process now, stdin sent to it is
processed in separate process and doesn't come back to
TestApp.actual_calls (self.app). Annotate tests for now, to be fixed
later.
Since we use qubes.VMShell service now and send requested command on its
stdin, we need to terminate that shell after requested command -
otherwise the service will not terminate automatically waiting for
further input (next commands).
