config: Support expansion in the Host variable too.
config: Support expansion in the Host variable too.

BUG: https://red.libssh.org/issues/127

mwgoldsmith/ssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/libssh