shtests: count nonexistent tests as errors (re: c2eabc57)

When a nonexistent test script was given as an argument to
shtests, this was not counted as an error and shtests exited
successfully (with status 0).

src/cmd/ksh93/tests/shtests:
- Increase total error count if a test script is not found.

src/cmd/ksh93/tests/shtests

@@ -305,6 +305,7 @@ for i in ${*-*.sh}
 do	[[ $i == *.sh ]] || i+='.sh'
 	if	[[ ! -r $i ]]
 	then	echo $0: $i: not found >&2
+		(( ++total_e ))
 		continue
 	fi
 	t=$(grep -c err_exit $i)