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/session_cmds.cpp b/command/session_cmds.cpp
index fb2d074..d363c1e 100644
--- a/command/session_cmds.cpp
+++ b/command/session_cmds.cpp
@@ -23,9 +23,8 @@
     response->completionCode = IPMI_CC_OK;
     uint8_t reqPrivilegeLevel = request->reqPrivLevel;
 
-    auto session = (std::get<session::Manager&>(singletonPool)
-                        .getSession(handler.sessionID))
-                       .lock();
+    auto session = std::get<session::Manager&>(singletonPool)
+                       .getSession(handler.sessionID);
 
     if (reqPrivilegeLevel == 0) // Just return present privilege level
     {