Do not clobber status before 'cond' expressions.

This spurious status reset must have been an attempt to make sure that
when no branch is taken, the status ends up as zero.  It is not
necessary and causes problems when trying to branch based on the value
of '$?'.

* geesh/shell.scm (sh:cond): Remove spurious 'set-status!'.

geesh/shell.scm

@@ -377,7 +377,6 @@ of each thunk sent to the input of the next thunk."
            (loop tail))))))
 
 (define (sh:cond . cases)
-  (set-status! 0)
   (let loop ((cases cases))
     (match cases
       (() (set-status! 0))