Fix some spelling errors in comment (#2533)

Signed-off-by: zhoulin xie <zhoulin.xie@daocloud.io>

plugin/etcd/msg/path.go

@@ -30,7 +30,7 @@ func Domain(s string) string {
 }
 
 // PathWithWildcard ascts as Path, but if a name contains wildcards (* or any), the name will be
-// chopped of before the (first) wildcard, and we do a highler evel search and
+// chopped of before the (first) wildcard, and we do a higher level search and
 // later find the matching names.  So service.*.skydns.local, will look for all
 // services under skydns.local and will later check for names that match
 // service.*.skydns.local.  If a wildcard is found the returned bool is true.