ZTS: Re-enable MMP tests

Commit 7fab6361 inadvertently disabled the MMP test cases by creating
and not removing an /etc/hostid file in the new zpool_split_props test
case.  When the file exists the ZTS skips the entire MMP test group
rather than modify what may be a system which is already configured.
Update the test case to remove the file.

Additionally, because the MMP tests were disabled a regression slipped
in as part of commit 9eb7b46ed0.  Fix it.

Reviewed-by: Tim Chase <tim@chase2k.com>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7514

tests/zfs-tests/tests/functional/cli_root/zpool_split/zpool_split_props.ksh

@@ -15,6 +15,7 @@
 #
 
 . $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/mmp/mmp.kshlib
 
 #
 # DESCRIPTION:
@@ -33,6 +34,7 @@ function cleanup
 	destroy_pool $TESTPOOL
 	destroy_pool $TESTPOOL2
 	rm -f $DEVICE1 $DEVICE2
+	log_must mmp_clear_hostid
 }
 
 function setup_mirror
@@ -45,6 +47,10 @@ function setup_mirror
 log_assert "'zpool split' can set new property values on the new pool"
 log_onexit cleanup
 
+if [ -e $HOSTID_FILE ]; then
+	log_unsupported "System has existing $HOSTID_FILE file"
+fi
+
 typeset good_props=('comment=text' 'ashift=12' 'multihost=on'
     'listsnapshots=on' 'autoexpand=on' 'autoreplace=on' 'dedupditto=1234'
     'delegation=off' 'failmode=continue')
@@ -57,7 +63,7 @@ DEVICE1="$TEST_BASE_DIR/device-1"
 DEVICE2="$TEST_BASE_DIR/device-2"
 
 # Needed to set multihost=on
-zgenhostid
+log_must mmp_set_hostid $HOSTID1
 
 # Verify we can set a combination of valid property values on the new pool
 for prop in "${good_props[@]}"
@@ -68,7 +74,10 @@ do
 	log_must zpool split -o $prop $TESTPOOL $TESTPOOL2
 	log_must zpool import -N -d $TEST_BASE_DIR $TESTPOOL2
 	log_must test "$(get_pool_prop $propname $TESTPOOL2)" == "$propval"
-	cleanup
+
+	destroy_pool $TESTPOOL
+	destroy_pool $TESTPOOL2
+	rm -f $DEVICE1 $DEVICE2
 done
 
 # Verify we cannot set invalid property values