lazycat-daemon/lazycatd.scm (handle-diff-req): Fix a bug.

* lazycat-daemon/lazycatd.scm (exec-cmd): Fix the debug trace.
  (handle-diff-req): Fix a bug: call `exec-cmd-on-host' instead of
  `lazycat-exec'.
ui/lc.scm (handle-diff): Fix a bug.

* ui/lc.scm (handle-diff): Fix a bug: rename `coninue?' to
  `continue?'.