Refactor: Simplify KVBucket::getRandomKey

There was a bug in KBBucket::getRandomKey - see MB-31495, which
although has been fixed highlighted unnecessary complexity in the
implementation of the function.

This patch simplfies the implementation of the function by removing
the nested while loops.

Change-Id: I614ef388abecf90992df31fbbd06d1b6ead5477e
Reviewed-on: http://review.couchbase.org/100397
Tested-by: Build Bot <[email protected]>
Reviewed-by: Paolo Cocchi <[email protected]>

Author: owend74

engines/ep/src/kv_bucket.cc

@@ -1413,28 +1413,17 @@ GetValue KVBucket::getRandomKey() {
 
     while (itm == NULL) {
         VBucketPtr vb = getVBucket(Vbid(curr++));
-        while (!vb || vb->getState() != vbucket_state_active) {
-            if (curr == max) {
-                curr = 0;
-            }
-            if (curr == start) {
-                return GetValue(NULL, ENGINE_KEY_ENOENT);
-            }
-
-            vb = getVBucket(Vbid(curr++));
-        }
-
-        if ((itm = vb->ht.getRandomKey(getRandom()))) {
+        if (vb && vb->getState() == vbucket_state_active &&
+                (itm = vb->ht.getRandomKey(getRandom()))) {
             GetValue rv(std::move(itm), ENGINE_SUCCESS);
             return rv;
         }
 
         if (curr == max) {
             curr = 0;
         }
-
         if (curr == start) {
-            return GetValue(NULL, ENGINE_KEY_ENOENT);
+            break;
         }
         // Search next vbucket
     }