utils/ipc-sshtunnel: Properly escape command passed to ssh

utils/ipc-sshtunnel: Properly escape command passed to ssh

When ipc-sshtunnel spawns ipc-tap and ipc-inject over ssh, it does
not correctly escape the arguments passed to ssh, causing arguments
to be expanded where no expansion is desired.

This commit modifies the way ipc-sshtunnel so that it correctly
quotes and escapes arguments that are passed to ssh.