qubes.VMShell service, used by qvm-run, expects the command on the first
input line. Previously, when --localcmd was used, the command wasn't
written anywhere and the local command was connected directly to
qubes.VMShell service. And the first line of its output was interpreted
as a command.
Fix this by starting the local command separately, after sending the
command to qubes.VMShell service.
While at it, unify handling shell command and service calls in the process.
vm.run_service(..., localcmd= ) isn't that useful in general case,
because for qubes.VMShell the caller first need to send the command
before starting local process. Since the qvm-run tool needs to implement
manual starting localcmd anyway, don't use localcmd= run_service's
argument at all to unify calling methods.
There is slight behavior change: previously localcmd was started only
after establishing service connection (for example only if qrexec policy
allows), now it is started in all the cases.
FixesQubesOS/qubes-issues#4040
9acce13a35