Initialize all the fields for the test kvstore (#982)

Follow up to https://github.com/valkey-io/valkey/pull/966, which didn't
update the kvstore tests. I'm not actually entirely clear why it fixes
it, but the consistency prevents the crash very reliably so will merge
it now and maybe see if Zhao has a better explanation.

---------

Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>

src/unit/test_kvstore.c

@@ -10,7 +10,15 @@ void freeTestCallback(dict *d, void *val) {
     zfree(val);
 }
 
-dictType KvstoreDictTestType = {hashTestCallback, NULL, NULL, freeTestCallback, NULL, NULL};
+dictType KvstoreDictTestType = {hashTestCallback,
+                                NULL,
+                                NULL,
+                                freeTestCallback,
+                                NULL,
+                                NULL,
+                                kvstoreDictRehashingStarted,
+                                kvstoreDictRehashingCompleted,
+                                kvstoreDictMetadataSize};
 
 char *stringFromInt(int value) {
     char buf[32];