os/bluestore: fix empty check

We want exists to be true if there is *any* old object that is not
in the onode_map or flagged as exists.  The previous code would only
tell us if the last-listed object was that way.

Signed-off-by: Sage Weil <sage@redhat.com>

src/os/bluestore/BlueStore.cc

@@ -13320,12 +13320,12 @@ int BlueStore::_remove_collection(TransContext *txc, const coll_t &cid,
       for (auto it = ls.begin(); !exists && it < ls.end(); ++it) {
         dout(10) << __func__ << " oid " << *it << dendl;
         auto onode = (*c)->onode_map.lookup(*it);
-        exists = !onode || onode->exists;
-        if (exists) {
+        if (!onode || onode->exists) {
           dout(1) << __func__ << " " << *it
 		  << " exists in db, "
 		  << (!onode ? "not present in ram" : "present in ram")
 		  << dendl;
+	  exists = true;
         }
       }
       if (!exists) {