ssh: fix flakey ssh errors on BSD systems There's been a persistent issue with flakiness on BSD systems (like OSX) where the 'no suitable response from remote hg' message would sometimes not appear. This was caused by one of the earlier calls failing with a "IOError: Broken pipe". Catching those errors and printing the same message removes the flakiness. Differential Revision: https://phab.mercurial-scm.org/D687