NEX-15891 Latest grep from illumos broke zvol_swap tests and swapadd
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Rob Gittins <rob.gittins@nexenta.com>

@@ -143,9 +143,9 @@
                 # added earlier uses the same name as something to be added
                 # later, the following test won't work. This should only happen
                 # if parts of a particular swap file are added or deleted by
                 # hand between invocations.
                 #
-                swap -l 2>/dev/null | grep '\<'${special}'\>' >/dev/null 2>&1 \
+                swap -l 2>/dev/null | grep -q "^$special " \
                     || swap -$PASS -a $special >/dev/null
         fi
 done