util/tests: initialize variable

This just silences a compiler-warning about a potentially uninitialized
variable. It's not uninitialized, but it's a bit hard for the compiler
to see. So let's just initialize it to zero.

Reviewed-by: Brian Paul <brianp@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4577>

src/util/tests/hash_table/random_entry.c

@@ -58,7 +58,7 @@ main(int argc, char **argv)
    struct hash_table *ht;
    struct hash_entry *entry;
    uint32_t keys[SIZE];
-   uint32_t i, random_value;
+   uint32_t i, random_value = 0;
 
    (void) argc;
    (void) argv;