librbd/internal.cc: close resource leak

Fix for:

CID 1295405 (yehudasa#1 of 1): Resource leak (RESOURCE_LEAK)
 leaked_storage: Variable req_comp going out of scope leaks
 the storage it points to.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>

src/librbd/internal.cc

@@ -3936,6 +3936,7 @@ int invoke_async_request(ImageCtx *ictx, const std::string& request_type,
                               req_comp);
       } else {
 	if(ictx->cct->_conf->rbd_skip_partial_discard) {
+	  delete req_comp;
 	  continue;
 	}
 	req = new AioZero(ictx, p->oid.name, p->objectno, p->offset, p->length,