netipmid: use std::shared_ptr instead of weak_ptr/lock

All of the instances of getSession and startSession were assigning the
result to a local shared_ptr via lock on the weak_ptr. It doesn't make
sense to demote the shared_ptr (from the sessionsMap) to a weak_ptr via
the return, only to promote to a shared_ptr again via lock.

Tested-by: running ipmitool -H a.b.c.d -P 0penBmc -I lanplus mc info
           Sessions start and stop, same as before.

Change-Id: Ic10779285891d73ee51115f16ed0000b38d1c52a
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/command/sol_cmds.cpp b/command/sol_cmds.cpp
index fb6f19e..a8fa410 100644
--- a/command/sol_cmds.cpp
+++ b/command/sol_cmds.cpp
@@ -57,8 +57,7 @@
     request->minorVersion = MINOR_VERSION;
 
     auto session =
-        (std::get<session::Manager&>(singletonPool).getSession(sessionID))
-            .lock();
+        std::get<session::Manager&>(singletonPool).getSession(sessionID);
 
     message::Handler msgHandler(session->channelPtr, sessionID);