Don't show error message in bro-cut when gawk not found

On some systems, the "which" command reports an error message on stderr
when the specified command is not found.  On these systems an error
message was always visible when running bro-cut when gawk is not found.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Don't show error message in bro-cut when gawk not found