limactl shell INSTANCE should show an explicit error

[AkihiroSuda]

limactl shell INSTANCE may fail e.g., when sshd in the guest is dead.

However, no error is shown currently.

$ limactl shell foo
$ echo $?
255

---

ssh_config(5)

     LogLevel
             Gives the verbosity level that is used when logging messages from ssh(1).  The possible values are:
             QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.  The default is INFO.  DEBUG and
             DEBUG1 are equivalent.  DEBUG2 and DEBUG3 each specify higher levels of verbose output.