contrib: don't use truncated names in fleetctl-inject-ssh.sh script

The fleetctl-inject-ssh.sh script currently tries to identify machines
with their truncated name, which now ends in '...'. Example:
'6efa03e8...'. When SSHing the error 'Requested machine could not be
found.' is returned.
Merge pull request #812 from zachlatta/patch-1

Fix fleetctl-inject-ssh.sh script