Fixed indentation.

Some lines (incorrectly) had an indentation of 3 or 5, or 7 or 9,
or 11 or 13, or 15 or 17 spaces instead of 4, 8, 12, or 16.  Fix them.

Found with:

$ find src -type f | xargs grep -n '^   [^ ]';
$ find src -type f | xargs grep -n '^     [^ *]';
$ find src -type f | xargs grep -n '^       [^ ]';
$ find src -type f | xargs grep -n '^         [^ *]';
$ find src -type f | xargs grep -n '^           [^ +]';
$ find src -type f | xargs grep -n '^             [^ *+]';
$ find src -type f | xargs grep -n '^               [^ +]';
$ find src -type f | xargs grep -n '^                 [^ *+]';

src/nxt_unit.c

@@ -5114,9 +5114,9 @@ nxt_unit_ctx_alloc(nxt_unit_ctx_t *ctx, void *data)
 
     rc = nxt_unit_ctx_init(lib, new_ctx, data);
     if (nxt_slow_path(rc != NXT_UNIT_OK)) {
-         nxt_unit_free(ctx, new_ctx);
+        nxt_unit_free(ctx, new_ctx);
 
-         return NULL;
+        return NULL;
     }
 
     queue_fd = -1;