Replace ISAINFO with is_32bit function

The isainfo(1) utility was used by the ZFS Test Suite to determine
when running on a 32-bit platform.  This non-portable check has been
replaced with an is_32bit helper function which uses getconf(1).
The getconf(1) utility is available for Linux, FreeBSD, and Illumos.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

tests/zfs-tests/include/commands.cfg.in

@@ -48,7 +48,6 @@ export HEAD="@HEAD@"
 export HOSTNAME="@HOSTNAME@"
 export ID="@ID@"
 export IOSTAT="@IOSTAT@"
-export ISAINFO="@ISAINFO@"
 export KILL="@KILL@"
 export KSH="@KSH@"
 export KSTAT="@KSTAT@"

tests/zfs-tests/tests/functional/cli_root/zfs_destroy/zfs_destroy_002_pos.ksh

@@ -73,7 +73,7 @@ if is_global_zone ; then
 	log_must $ZFS create -V $VOLSIZE $TESTPOOL/$TESTVOL
 
 	# Max volume size is 1TB on 32-bit systems
-	[[ $($ISAINFO -b) == 32 ]] && \
+	[[ is_32bit ]] && \
 		BIGVOLSIZE=1Tb
 	log_must $ZFS create -sV $BIGVOLSIZE $TESTPOOL/$TESTVOL1
 fi

tests/zfs-tests/tests/functional/largest_pool/largest_pool_001_pos.ksh

@@ -126,7 +126,7 @@ for volsize in $VOLSIZES; do
 	str=$($ZFS create -sV $volsize $TESTPOOL2/$TESTVOL 2>&1)
 	ret=$?
 	if (( ret != 0 )); then
-		if [[ $($ISAINFO -b) == 32 && \
+		if [[ is_32bit && \
 			$str == *${VOL_LIMIT_KEYWORD1}* || \
 			$str == *${VOL_LIMIT_KEYWORD2}* || \
 			$str == *${VOL_LIMIT_KEYWORD3}* ]]