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>
11 files changed