netipmid: make session a header-only situation

The Session class is a fairly simple class, no need for an external cpp
file; make it all header-only and allow the compiler to do its job.

Change-Id: Ibbe7e963762926ec04c75ab187a5b8045de851f4
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/session.hpp b/session.hpp
index 338a815..4ba3fa6 100644
--- a/session.hpp
+++ b/session.hpp
@@ -231,7 +231,31 @@
      * transaction time is compared against the session inactivity timeout.
      *
      */
-    bool isSessionActive();
+    bool isSessionActive()
+    {
+        auto currentTime = std::chrono::steady_clock::now();
+        auto elapsedSeconds = std::chrono::duration_cast<std::chrono::seconds>(
+            currentTime - lastTime);
+
+        switch (state)
+        {
+            case State::SETUP_IN_PROGRESS:
+                if (elapsedSeconds < SESSION_SETUP_TIMEOUT)
+                {
+                    return true;
+                }
+                break;
+            case State::ACTIVE:
+                if (elapsedSeconds < SESSION_INACTIVITY_TIMEOUT)
+                {
+                    return true;
+                }
+                break;
+            default:
+                return false;
+        }
+        return false;
+    }
 
     /**
      * @brief Session's Current Privilege Level