parser: match on length of argument, not potential value

Otherwise we match subset of a string, that doesn't always
work well.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/parse.c b/parse.c
index ad2b1e3..869bcda 100644
--- a/parse.c
+++ b/parse.c
@@ -299,7 +299,7 @@
 			if (!vp->ival || vp->ival[0] == '\0')
 				continue;
 			all_skipped = 0;
-			if (!strncmp(vp->ival, ptr, strlen(vp->ival))) {
+			if (!strncmp(vp->ival, ptr, strlen(ptr))) {
 				ret = 0;
 				if (o->roff1) {
 					if (vp->or)