tri: exact matches are never ambiguous

Even when the exact match is a prefix of a longer match.

src/common/tri.c

@@ -113,6 +113,10 @@ void *tri_get_string_autocomplete(struct tri *tri, const char *string, bool *amb
 		node = node->nodes[idx];
 	}
 
+	if (node->value) {
+		return node->value;
+	}
+
 	while(1) {
 		struct tri_node *next_node = NULL;
 		int num_paths = 0;