Avoid a delay at startup when concurrency is enabled and there are
rsync or gcrypt special remotes, which was caused by git-annex
opening a ssh connection to the remote too early.
sshOptions makes a connection to the ssh server if one is not already open,
when concurrency is enabled. Avoid doing that at startup, when the remote
list is being built, but the remote may not be used at all.
Instead, rsync/gcrypt now runs sshOptions once per ssh connection to the
server. This should not be significant overhead since Remote.Git already
has the same overhead (as do Bup and Ddar).
44de3fff0b