ldmsd_row_cache: fix tree_comparator() function

Fix the tree_comparator function to continue on to comparing
the following keys if the current keys are equal.

ldms/src/ldmsd/ldmsd_row_cache.c

@@ -40,6 +40,7 @@ static int tree_comparator(void *a, const void *b)
 	ldmsd_row_cache_idx_t key_a = (ldmsd_row_cache_idx_t)a;
 	ldmsd_row_cache_idx_t key_b = (ldmsd_row_cache_idx_t)b;
 	ldmsd_row_cache_key_t rowk_a, rowk_b;
+        int rc;
         assert(key_a->key_count == key_b->key_count);
 	for (i = 0; i < key_a->key_count; i++) {
 		rowk_a = key_a->keys[i];
@@ -55,10 +56,13 @@ static int tree_comparator(void *a, const void *b)
 				return -1;
 			if (rowk_a->mval->v_ts.usec > rowk_b->mval->v_ts.usec)
 				return 1;
-			return 0;
+                        continue;
 		case LDMS_V_CHAR_ARRAY:
-			return strncmp(rowk_a->mval->a_char, rowk_b->mval->a_char,
-				       rowk_a->count);
+			rc = strncmp(rowk_a->mval->a_char, rowk_b->mval->a_char,
+                                     rowk_a->count);
+                        if (rc != 0)
+                                return rc;
+                        continue;
 		case LDMS_V_CHAR:
 			if (rowk_a->mval->v_char == rowk_b->mval->v_char)
 				continue;