Add a shell helper function to wait for some command to succeed - typically
a test for something to be done by a background process. Use it in the
context code which waits for the guest to respond to ssh-over-vsock
connections.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>