Mesh: Apply Fixes & code refactoring

Mesh: Apply Fixes & code refactoring

This patch handles initial set of fixes
across all layers in BLE Mesh FRWK & some
code refactoring

Some of the notable fixes applied are following:-
1. Fix bt-service crash during cleanup of mesh framework resources
   [Resolution: removing double free of Mesh model resources]
2. Fix crash in unit test app during Scan stop operation
   [Resolution: Dont allow Stop scan if scanning is not in progress]
3. Fix Node Browse event fail issue
   [Resolution: Handle wrong usage of event pointer]
4. Fix "Timer expired even if response is received within timeout" issue.
   [Resolution: Remove timer once event is received from stack]
5. Fix "TTL configured callback(CAPI callback)" is not invoked in case of success
   Resolution: Handle wrong usage of event pointer in service layer]
6. Fix NetKey configuration API failed due to mishandling of Key in Network
   [Resolution: Network Key handling is corrected]

Change-Id: I107a1d26df134d54a7347e4cae71a38e106b6a12
Signed-off-by: Anupam Roy <anupam.r@samsung.com>