Removed main.h dependency from rpcserver.cpp

Rebased by @laanwj:

- update for RPC methods added since 84d13ee: setmocktime,
  invalidateblock, reconsiderblock. Only the first, setmocktime, required a change,
  the other two are thread safe.

src/rpcnet.cpp

@@ -34,7 +34,8 @@ Value getconnectioncount(const Array& params, bool fHelp)
             + HelpExampleRpc("getconnectioncount", "")
         );
 
-    LOCK(cs_vNodes);
+    LOCK2(cs_main, cs_vNodes);
+
     return (int)vNodes.size();
 }
 
@@ -52,7 +53,8 @@ Value ping(const Array& params, bool fHelp)
         );
 
     // Request that each node send a ping during next message processing pass
-    LOCK(cs_vNodes);
+    LOCK2(cs_main, cs_vNodes);
+
     BOOST_FOREACH(CNode* pNode, vNodes) {
         pNode->fPingQueued = true;
     }
@@ -113,6 +115,8 @@ Value getpeerinfo(const Array& params, bool fHelp)
             + HelpExampleRpc("getpeerinfo", "")
         );
 
+    LOCK(cs_main);
+
     vector<CNodeStats> vstats;
     CopyNodeStats(vstats);
 
@@ -411,6 +415,8 @@ Value getnetworkinfo(const Array& params, bool fHelp)
             + HelpExampleRpc("getnetworkinfo", "")
         );
 
+    LOCK(cs_main);
+
     Object obj;
     obj.push_back(Pair("version",       CLIENT_VERSION));
     obj.push_back(Pair("subversion",