Update IPMI max session count from 5 to 15

According to the IPMI spec,No of possible active session is
one byte - BIT5-BIT0 so 63 is the max active session we can have.

- 15 was chosen as it seems to be reasonable.

Tested: Able to establish the 14 LAN sessions and 1 reserved for
sessionless connection.
Get session Info command should provide 15 as max no of ipmi session

Signed-off-by: Suryakanth Sekar <suryakanth.sekar@linux.intel.com>
Change-Id: I1bc2003502f35c1d15de18cdf2874cd6ce74006e
diff --git a/sessions_manager.hpp b/sessions_manager.hpp
index 251ca96..9fd38b1 100644
--- a/sessions_manager.hpp
+++ b/sessions_manager.hpp
@@ -17,7 +17,7 @@
 
 constexpr size_t SESSION_ZERO = 0;
 constexpr size_t MAX_SESSIONLESS_COUNT = 1;
-constexpr size_t MAX_SESSION_COUNT = 5;
+constexpr size_t MAX_SESSION_COUNT = 15;
 
 /**
  * @class Manager