config.c: Avoid leaking file handle if redis_fstat() fails (#12796)

If fopen() is successful, but redis_fstat() fails, the file handle
stored in fp will leak. This change closes the filehandle stored in fp
if redis_fstat() fails.

Fixes Coverity 390029

src/config.c

@@ -1120,7 +1120,10 @@ struct rewriteConfigState *rewriteConfigReadOldFile(char *path) {
     if (fp == NULL && errno != ENOENT) return NULL;
 
     struct redis_stat sb;
-    if (fp && redis_fstat(fileno(fp),&sb) == -1) return NULL;
+    if (fp && redis_fstat(fileno(fp),&sb) == -1) {
+        fclose(fp);
+        return NULL;
+    }
 
     int linenum = -1;
     struct rewriteConfigState *state = rewriteConfigCreateState();