12181 zvol swap tests should avoid grep -w

@@ -26,10 +26,11 @@
 #
 
 #
 # Copyright (c) 2013, 2016 by Delphix. All rights reserved.
 # Copyright 2016 Nexenta Systems, Inc.
+# Copyright 2020 Joyent, Inc.
 #
 
 . $STF_SUITE/include/libtest.shlib
 . $STF_SUITE/tests/functional/zvol/zvol_common.shlib
 

@@ -52,11 +53,12 @@
         typeset dumpdev=$(get_dumpdevice)
         if [[ $dumpdev != $savedumpdev ]] ; then
                 safe_dumpadm $savedumpdev
         fi
 
-        swap -l | grep -w $voldev > /dev/null 2>&1
+        swap -l | awk 'NR > 1 { print $1 }' | \
+            grep "^$voldev\$" > /dev/null 2>&1
         if (( $? == 0 ));  then
                 log_must swap -d $voldev
         fi
 
         typeset snap