Add test to check new importmulti "now" value

Easiest way to test this was to expose the timestamp via the validateaddress
RPC (which was already looking up and returning key metadata).

qa/rpc-tests/importmulti.py

@@ -139,6 +139,7 @@ class ImportMultiTest (BitcoinTestFramework):
         # Address + Private key + !watchonly
         print("Should import an address with private key")
         address = self.nodes[0].validateaddress(self.nodes[0].getnewaddress())
+        timestamp = self.nodes[1].getblock(self.nodes[1].getbestblockhash())['time']
         result = self.nodes[1].importmulti([{
             "scriptPubKey": {
                 "address": address['address']
@@ -150,6 +151,7 @@ class ImportMultiTest (BitcoinTestFramework):
         address_assert = self.nodes[1].validateaddress(address['address'])
         assert_equal(address_assert['iswatchonly'], False)
         assert_equal(address_assert['ismine'], True)
+        assert_equal(address_assert['timestamp'], timestamp)
 
         # Address + Private key + watchonly
         print("Should not import an address with private key and with watchonly")

src/rpc/misc.cpp

@@ -167,6 +167,7 @@ UniValue validateaddress(const JSONRPCRequest& request)
             "  \"pubkey\" : \"publickeyhex\",    (string) The hex value of the raw public key\n"
             "  \"iscompressed\" : true|false,  (boolean) If the address is compressed\n"
             "  \"account\" : \"account\"         (string) DEPRECATED. The account associated with the address, \"\" is the default account\n"
+            "  \"timestamp\" : timestamp,        (number, optional) The creation time of the key if available in seconds since epoch (Jan 1 1970 GMT)\n"
             "  \"hdkeypath\" : \"keypath\"       (string, optional) The HD keypath if the key is HD and available\n"
             "  \"hdmasterkeyid\" : \"<hash160>\" (string, optional) The Hash160 of the HD master pubkey\n"
             "}\n"
@@ -204,10 +205,16 @@ UniValue validateaddress(const JSONRPCRequest& request)
         if (pwalletMain && pwalletMain->mapAddressBook.count(dest))
             ret.push_back(Pair("account", pwalletMain->mapAddressBook[dest].name));
         CKeyID keyID;
-        if (pwalletMain && address.GetKeyID(keyID) && pwalletMain->mapKeyMetadata.count(keyID) && !pwalletMain->mapKeyMetadata[keyID].hdKeypath.empty())
-        {
-            ret.push_back(Pair("hdkeypath", pwalletMain->mapKeyMetadata[keyID].hdKeypath));
-            ret.push_back(Pair("hdmasterkeyid", pwalletMain->mapKeyMetadata[keyID].hdMasterKeyID.GetHex()));
+        if (pwalletMain) {
+            const auto& meta = pwalletMain->mapKeyMetadata;
+            auto it = address.GetKeyID(keyID) ? meta.find(keyID) : meta.end();
+            if (it != meta.end()) {
+                ret.push_back(Pair("timestamp", it->second.nCreateTime));
+                if (!it->second.hdKeypath.empty()) {
+                    ret.push_back(Pair("hdkeypath", it->second.hdKeypath));
+                    ret.push_back(Pair("hdmasterkeyid", it->second.hdMasterKeyID.GetHex()));
+                }
+            }
         }
 #endif
     }