t_create.sh: use ATF_TESTS_SH_SED & remove local mods

This particular change replaces all local modifications to the test
script like so:
- Use `ATF_TESTS_SH_SED_test` with a sed(1) statement in the Makefile,
  instead of the equivalent local modifications.
- Remove the need for expecting the output of newfs_msdos to be empty.
  There isn't much to gain from deviating from the upstream NetBSD test--it's
  just another local modification that would need to be carried forward. If
  it's worth testing this FreeBSD-specific behavior, it should be in a
  FreeBSD-specific test.

This makes moving new modifications to the script easier moving forward.

MFC after:	1 week

contrib/netbsd-tests/sbin/newfs_msdos/t_create.sh

@@ -31,21 +31,11 @@ validfat32_head() {
 }
 validfat32_body() {
 
-	if true; then
-		# FreeBSD
-		exp_err=empty
-		fsck=fsck_msdosfs
-	else
-		# NetBSD
-		exp_err=ignore
-		fsck=fsck_msdos
-	fi
-
-	atf_check -s eq:0 -o ignore -e $exp_err \
+	atf_check -s eq:0 -o ignore -e ignore \
 	    newfs_msdos -b 512 -C 33m -F 32 msdos.img
 #	fsck_msdos/newfs_msdos have been fixed
 #	atf_expect_fail "PR bin/46743"
-	atf_check -s eq:0 -o not-match:FIXED -e empty $fsck -p msdos.img
+	atf_check -s eq:0 -o not-match:FIXED -e empty fsck_msdos -p msdos.img
 	atf_expect_pass
 }
 

sbin/newfs_msdos/tests/Makefile

@@ -2,5 +2,7 @@ TESTSRC=${SRCTOP}/contrib/netbsd-tests/sbin/newfs_msdos
 
 NETBSD_ATF_TESTS_SH+=	create
 
+ATF_TESTS_SH_SED_create=	-e 's/fsck_msdos/fsck_msdosfs/'
+
 .include <netbsd-tests.test.mk>
 .include <bsd.test.mk>