ssh-proxy.scm (make-new-session): Improve conditionals a bit.

* proxies/ssh-proxy.scm (make-new-session): Improve conditionals a
  bit.
curiosity.scm: Rename global immutable variables.

* lazycat-daemon/curiosity.scm (*curiosity-thread-prio*): Rename
  to `%curiosity-thread-prio'.
  (*lsb-release-cmd*): Rename to `%lsb-release-cmd'.