ZTS: Fix refreserv_raidz.ksh

The rerefreserv_raidz test was failing on Linux because the sync being
issued doesn't guarantee a pool sync.  Switch to using the sync_pool
function and remove the ZTS exception for Linux.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #12897

tests/test-runner/bin/zts-report.py.in

@@ -285,7 +285,6 @@ elif sys.platform.startswith('linux'):
         'mmp/mmp_active_import': ['FAIL', known_reason],
         'mmp/mmp_exported_import': ['FAIL', known_reason],
         'mmp/mmp_inactive_import': ['FAIL', known_reason],
-        'refreserv/refreserv_raidz': ['FAIL', known_reason],
         'snapshot/rollback_003_pos': ['FAIL', known_reason],
     })
 

tests/zfs-tests/tests/functional/refreserv/refreserv_raidz.ksh

@@ -110,7 +110,7 @@ for parity in 1 2 3; do
 			block_device_wait "/dev/zvol/$vol"
 			log_must dd if=/dev/zero of=/dev/zvol/$vol \
 			    bs=1024k count=$volsize
-			sync
+			sync_pool $TESTPOOL
 
 			ref=$(zfs get -Hpo value referenced "$vol")
 			refres=$(zfs get -Hpo value refreservation "$vol")