Merge #14556: qt: fix confirmed transaction labeled "open" (#13299)

fb3ce75807 Don't label transactions "Open" while catching up (Hennadii Stepanov)

Pull request description:

  Fix #13299.

  Since the default `nSequence` is `0xFFFFFFFE` and locktime is enabled, the checking `wtx.is_final` is meaningless until the syncing has completed (ref: #1026).

  This PR makes the wallet mark a transaction "Unconfirmed" instead of misleading "Open for NNN more blocks" when syncing after a period of being offline.

  Before this PR (with the issue):
  ![screenshot from 2018-12-12 15-56-23](https://user-images.githubusercontent.com/32963518/49874288-cdd06880-fe26-11e8-8441-f3ceb479611b.png)

  With this PR (the issue has been resolved):
  ![screenshot from 2018-12-12 15-54-41](https://user-images.githubusercontent.com/32963518/49874336-e9d40a00-fe26-11e8-8c05-9aeee2eb1bba.png)

Tree-SHA512: 358ec83b43c266a4d32a37a79dda80e80d40a2b77ad38261c84a095e613399f674aa7184805b3f6310e51ddb83ae2636b8849fcc7c4333e1b3ecbb0f70ad86d3

src/interfaces/wallet.cpp

@@ -318,7 +318,8 @@ public:
     }
     bool tryGetTxStatus(const uint256& txid,
         interfaces::WalletTxStatus& tx_status,
-        int& num_blocks) override
+        int& num_blocks,
+        int64_t& block_time) override
     {
         auto locked_chain = m_wallet.chain().lock(true /* try_lock */);
         if (!locked_chain) {
@@ -333,6 +334,7 @@ public:
             return false;
         }
         num_blocks = ::chainActive.Height();
+        block_time = ::chainActive.Tip()->GetBlockTime();
         tx_status = MakeWalletTxStatus(*locked_chain, mi->second);
         return true;
     }

src/interfaces/wallet.h

@@ -178,7 +178,8 @@ public:
     //! Try to get updated status for a particular transaction, if possible without blocking.
     virtual bool tryGetTxStatus(const uint256& txid,
         WalletTxStatus& tx_status,
-        int& num_blocks) = 0;
+        int& num_blocks,
+        int64_t& block_time) = 0;
 
     //! Get transaction details.
     virtual WalletTx getWalletTxDetails(const uint256& txid,