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/inheritance/inherit.kshlib

@@ -34,18 +34,12 @@
 #
 function get_prop_src # property dataset
 {
-        typeset prop_val
         typeset prop=$1
         typeset dataset=$2
 
-	prop_val=`zfs get -H -o source $prop $dataset`
-
-        if [[ $? -ne 0 ]]; then
-                log_fail "Unable to determine the source of $prop " \
+	zfs get -H -o source $prop $dataset ||
+                log_fail "Unable to determine the source of $prop" \
                         "property for dataset $dataset"
-        else
-                echo $prop_val
-        fi
 }
 
 #
@@ -63,7 +57,7 @@ function verify_prop_src # child_dataset property expected_src
         typeset prop=$2
         typeset expected=$3
 
-        prop_src=`get_prop_src $prop $target`
+        prop_src=$(get_prop_src $prop $target)
 
 	#
 	# Rather than just checking if $prop_src == $expected
@@ -105,7 +99,7 @@ function set_n_verify_prop #property value dataset
 	typeset dataset=$3
 
 	zfs set $prop=$prop_val $dataset
-	check_val=`get_prop $prop $dataset`
+	check_val=$(get_prop $prop $dataset)
 
 	if [[ $check_val != $prop_val ]]; then
 		log_fail "Property $prop of $dataset has value $check_val"\

tests/zfs-tests/tests/functional/inheritance/inherit_001_pos.ksh

@@ -337,9 +337,7 @@ function scan_state { #state-file
 
 					for p in ${prop[i]} ${prop[((i+1))]}; do
 						zfs $op $p $target
-						ret=$?
-						check_failure $ret "zfs $op $p \
-						    $target"
+						check_failure $? "zfs $op $p $target"
 					done
 				fi
 				for check_obj in $list; do
@@ -349,16 +347,14 @@ function scan_state { #state-file
 					# check_failure to keep journal small
 						verify_prop_src $check_obj $p \
 						    $final_src
-						ret=$?
-						check_failure $ret "verify" \
+						check_failure $? "verify" \
 						    "_prop_src $check_obj $p" \
 						    "$final_src"
 
 					# Again, to keep journal size down.
 						verify_prop_val $p $check_obj \
 						    $final_src $j
-						ret=$?
-						check_failure $ret "verify" \
+						check_failure $? "verify" \
 						    "_prop_val $check_obj $p" \
 						    "$final_src"
 					done