tests: review every instance of $?

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13259

tests/zfs-tests/tests/functional/xattr/setup.ksh

@@ -34,8 +34,7 @@
 # (it can cause useradd to take a long time, hitting our TIMEOUT)
 if is_illumos; then
 	USES_NIS=false
-	svcs svc:/network/nis/client:default | grep online > /dev/null
-	if [ $? -eq 0 ]
+	if svcs svc:/network/nis/client:default | grep -q online
 	then
 		svcadm disable -t svc:/network/nis/client:default
 		USES_NIS=true

tests/zfs-tests/tests/functional/xattr/xattr_011_pos.ksh

@@ -126,12 +126,8 @@ if is_illumos; then
 	log_must mkdir $TESTDIR/noxattrs
 	log_must touch $TESTDIR/noxattrs/no-xattr
 
-	find $TESTDIR -xattr | grep myfile.$$
-	[[ $? -ne 0 ]] && \
-		log_fail "find -xattr didn't find our file that had an xattr."
-	find $TESTDIR -xattr | grep no-xattr
-	[[ $? -eq 0 ]] && \
-		log_fail "find -xattr found a file that didn't have an xattr."
+	log_must eval "find $TESTDIR -xattr | grep -q myfile.$$"
+	log_mustnot eval "find $TESTDIR -xattr | grep -q no-xattr"
 	log_must rm -rf $TESTDIR/noxattrs
 else
 	log_note "Checking find - unsupported"

tests/zfs-tests/tests/functional/xattr/xattr_013_pos.ksh

@@ -52,12 +52,6 @@ function cleanup {
 log_assert "The noxattr mount option functions as expected"
 log_onexit cleanup
 
-zfs set 2>&1 | grep xattr > /dev/null
-if [ $? -ne 0 ]
-then
-	log_unsupported "noxattr mount option not supported on this release."
-fi
-
 log_must touch $TESTDIR/myfile.$$
 create_xattr $TESTDIR/myfile.$$ passwd /etc/passwd