THRIFT-3067 C++ cppcheck performance related warnings

Patch: Arijit Chattopadhyay <arijitnit06@gmail.com>

This closes #444
diff --git a/contrib/fb303/TClientInfo.cpp b/contrib/fb303/TClientInfo.cpp
index 5959fb1..1fc6612 100644
--- a/contrib/fb303/TClientInfo.cpp
+++ b/contrib/fb303/TClientInfo.cpp
@@ -154,9 +154,8 @@
     }
 
     timespec start;
-    double secs = 0.0;
     info->getTime(&start);
-    secs = (double)(now.tv_sec - start.tv_sec) + (now.tv_nsec - start.tv_nsec)*0.000000001;
+    double secs = (double)(now.tv_sec - start.tv_sec) + (now.tv_nsec - start.tv_nsec)*0.000000001;
 
     char buf[256];
     snprintf(buf, sizeof buf, "%d %s %s %.3f %llu", i, addrStr, callStr, secs,
diff --git a/contrib/fb303/cpp/FacebookBase.cpp b/contrib/fb303/cpp/FacebookBase.cpp
index 8003340..3c56975 100644
--- a/contrib/fb303/cpp/FacebookBase.cpp
+++ b/contrib/fb303/cpp/FacebookBase.cpp
@@ -98,7 +98,7 @@
   // want our read/write structure to go over the wire
   counters_.acquireRead();
   for(ReadWriteCounterMap::iterator it = counters_.begin();
-      it != counters_.end(); it++)
+      it != counters_.end(); ++it)
   {
     _return[it->first] = it->second.value;
   }
diff --git a/contrib/fb303/cpp/ServiceTracker.cpp b/contrib/fb303/cpp/ServiceTracker.cpp
index 2914ff6..7a61b21 100644
--- a/contrib/fb303/cpp/ServiceTracker.cpp
+++ b/contrib/fb303/cpp/ServiceTracker.cpp
@@ -251,7 +251,7 @@
   uint64_t count;
   for (iter = checkpointServiceDuration_.begin();
        iter != checkpointServiceDuration_.end();
-       iter++) {
+       ++iter) {
     count = iter->second.first;
     handler_->setCounter(string("checkpoint_count_") + iter->first, count);
     if (count == 0) {