OpenZFS 9185 - Enable testing over NFS in ZFS performance tests

This change makes additions to the ZFS test suite that allows the
performance tests to run over NFS. The test is run and performance data
collected from the server side, while IO is generated on the NFS client.

This has been tested with Linux and illumos NFS clients.

Authored by: Ahmed Ghanem <ahmedg@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Kevin Greene <kevin.greene@delphix.com>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: John Kennedy <john.kennedy@delphix.com>

OpenZFS-issue: https://www.illumos.org/issues/9185
Closes #8367

scripts/zfs-tests.sh

@@ -273,6 +273,7 @@ OPTIONS:
 	-f          Use files only, disables block device tests
 	-S          Enable stack tracer (negative performance impact)
 	-c          Only create and populate constrained path
+	-n NFSFILE  Use the nfsfile to determine the NFS configuration
 	-I NUM      Number of iterations
 	-d DIR      Use DIR for files and loopback devices
 	-s SIZE     Use vdevs of SIZE (default: 4G)
@@ -295,7 +296,7 @@ $0 -x
 EOF
 }
 
-while getopts 'hvqxkfScd:s:r:?t:T:u:I:' OPTION; do
+while getopts 'hvqxkfScn:d:s:r:?t:T:u:I:' OPTION; do
 	case $OPTION in
 	h)
 		usage
@@ -324,6 +325,12 @@ while getopts 'hvqxkfScd:s:r:?t:T:u:I:' OPTION; do
 		constrain_path
 		exit
 		;;
+	n)
+		nfsfile=$OPTARG
+		[[ -f $nfsfile ]] || fail "Cannot read file: $nfsfile"
+		export NFS=1
+		. "$nfsfile"
+		;;
 	d)
 		FILEDIR="$OPTARG"
 		;;