net: Consistently use GetTimeMicros() for inactivity checks

The use of mocktime in test logic means that comparisons between
GetTime() and GetTimeMicros()/1000000 are unreliable since the former
can use mocktime values while the latter always gets the system clock;
this changes the networking code's inactivity checks to consistently
use the system clock for inactivity comparisons.

Also remove some hacks from setmocktime() that are no longer needed,
now that we're using the system clock for nLastSend and nLastRecv.

src/rpc/misc.cpp

@@ -431,22 +431,16 @@ UniValue setmocktime(const JSONRPCRequest& request)
     if (!Params().MineBlocksOnDemand())
         throw runtime_error("setmocktime for regression testing (-regtest mode) only");
 
-    // cs_vNodes is locked and node send/receive times are updated
-    // atomically with the time change to prevent peers from being
-    // disconnected because we think we haven't communicated with them
-    // in a long time.
+    // For now, don't change mocktime if we're in the middle of validation, as
+    // this could have an effect on mempool time-based eviction, as well as
+    // IsCurrentForFeeEstimation() and IsInitialBlockDownload().
+    // TODO: figure out the right way to synchronize around mocktime, and
+    // ensure all callsites of GetTime() are accessing this safely.
     LOCK(cs_main);
 
     RPCTypeCheck(request.params, boost::assign::list_of(UniValue::VNUM));
     SetMockTime(request.params[0].get_int64());
 
-    uint64_t t = GetTime();
-    if(g_connman) {
-        g_connman->ForEachNode([t](CNode* pnode) {
-            pnode->nLastSend = pnode->nLastRecv = t;
-        });
-    }
-
     return NullUniValue;
 }