ssh connection should use "IdentitiesOnly yes" option

[dmd]

In some circumstances if your ssh-agent has a lot of keys, connecting fails e.g.:

Select the instance you want to connect to:

       INSTANCE                                │ TAG-KEY │ TAG-VALUE
     ──────────────────────────────────────────┼─────────┼────────────
   >   rt-dockertest12343(i-06ab0e3ff8715cad5) │         │
Connecting to instance failed: exit status 255Received disconnect from 34.236.152.159 port 22:2: Too many authentication failures
Disconnected from 34.236.152.159 port 22

A similar thing happens when trying to use the normal cli ssh command.

This issue is solved on the ssh command line with -o "IdentitiesOnly yes"; it would be good for this to also pass that option.