Merge #15248: rpc: Compile on GCC4.8

fa5f890 rpc: Compile on GCC4.8 (MarcoFalke)

Pull request description:

  GCC 4.8 is lacking some C++11 signatures (see "Adjust C++11 signatures to take a const_iterator." in GCC 4.9: gcc-mirror/gcc@3d2b2f4)

  Fix that by changing the code to use the pre-GCC 4.9 signature.

  Can be reverted after #13356.

  Fixes #15172 (reports on `Linux Mint 17.3 Rosa` and `CentOS Linux release 7.5.1804 (Core)`)

Tree-SHA512: 0c0b18968270ad4fcd0c2000c57485be881a461135dac3ad0bdab22c1a2292cf6b28ebeb930ccaa0290ff20ce87547fd07ab8189c4c4fb54d652a3d0bc9615f8

Author: MarcoFalke

src/rpc/server.cpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2010 Satoshi Nakamoto
-// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -51,7 +51,7 @@ struct RPCCommandExecution
     explicit RPCCommandExecution(const std::string& method)
     {
         LOCK(g_rpc_server_info.mutex);
-        it = g_rpc_server_info.active_commands.insert(g_rpc_server_info.active_commands.cend(), {method, GetTimeMicros()});
+        it = g_rpc_server_info.active_commands.insert(g_rpc_server_info.active_commands.end(), {method, GetTimeMicros()});
     }
     ~RPCCommandExecution()
     {