Post Fix to Bug#14628410 - ASSERTION `! IS_SET()' FAILED IN

			    DIAGNOSTICS_AREA::SET_OK_STATUS

Test fails on 5.1 valgrind build. This is because of close(-1)
system call.

Fixed by adding extra checks for valid file descriptor.

Approved by Vasil(Calvin). rb#1792

storage/innodb_plugin/row/row0merge.c

@@ -2642,6 +2642,14 @@ row_merge_build_indexes(
 	block_size = 3 * sizeof *block;
 	block = os_mem_alloc_large(&block_size);
 
+	/* Initialize all the merge file descriptors, so that we
+	don't call row_merge_file_destroy() on uninitialized
+	merge file descriptor */
+
+	for (i = 0; i < n_indexes; i++) {
+		merge_files[i].fd = -1;
+	}
+
 	for (i = 0; i < n_indexes; i++) {
 
 		if (row_merge_file_create(&merge_files[i]) < 0)
@@ -2699,7 +2707,9 @@ row_merge_build_indexes(
 	}
 
 func_exit:
+	if (tmpfd >= 0) {
 		close(tmpfd);
+	}
 
 	for (i = 0; i < n_indexes; i++) {
 		row_merge_file_destroy(&merge_files[i]);