Don't reset signal handlers inside handlers.

Don't reset signal handlers inside handlers.

The signal handlers from the original ssh1 code on which OpenSSH
is based assume unreliable signals and reinstall their handlers.
Since OpenBSD (and pretty much every current system) has reliable
signals this is not needed.  In the unlikely even that -portable
is still being used on such systems we will deal with it in the
compat layer.  ok deraadt@