CBD-6348: [BP] Fix ambiguous == operator in unit test

By casting to DocKey

    error: use of overloaded operator '==' is ambiguous (with operand types 'const StoredDocKeyT<std::allocator>' and 'const SerialisedDocKey')

Change-Id: If722de4964d2806745056924aaeb37cb008b6acc
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/234980
Reviewed-by: Trond Norbye <[email protected]>
Well-Formed: Restriction Checker
Tested-by: Trond Norbye <[email protected]>

Author: trondn

engines/ep/tests/module_tests/mutation_log_test.cc

@@ -666,10 +666,12 @@ TEST_F(MutationLogTest, upgradeV3toV4) {
         }
     };
 
+    const auto somekey = makeStoredDocKey("somekey");
+
     {
         MockMutationLog ml(tmp_log_filename, MutationLogVersion::V3);
         ml.open();
-        ml.newItem(Vbid(3), makeStoredDocKey("somekey"));
+        ml.newItem(Vbid(3), somekey);
         ml.commit1();
         ml.commit2();
         ml.flush();
@@ -682,7 +684,7 @@ TEST_F(MutationLogTest, upgradeV3toV4) {
         ASSERT_EQ(MutationLogVersion::V3, ml.header().version());
         auto iter = ml.begin();
         EXPECT_EQ(MutationLogType::New, (*iter)->type());
-        EXPECT_EQ(makeStoredDocKey("somekey"), (*iter)->key());
+        EXPECT_EQ(static_cast<const DocKey&>(somekey), (*iter)->key());
         ++iter;
         EXPECT_EQ(MutationLogType::Commit1, (*iter)->type());
         ++iter;