This reimplements parts of commit da0a4f8d1f
in a different, but compatible way.
We pass guestfs_vmchannel=tcp:<ip>:<port> on the command line. This
is intended to be used as follows (now and in future versions):
tcp:10.0.2.4:6666 for guestfwd vmchannel
tcp:10.0.2.2:<port> for future "no vmchannel" implementation
/dev/vcon4 for future virtio-console vmchannel*
It also accepts the old-style guestfs=10.0.2.4:6666 parameter which
is sent by older libraries, and turns this transparently into the
correct format above.
If no guestfs_vmchannel is passed, then this defaults to the guestfwd
vmchannel which older libraries would expect.
* Maybe this last one should be dev:/dev/vcon4 or file:/dev/vcon4, but
we don't need to decide that now.
8b217a87bf