Mesh: Fix bug in callback handling

Mesh: Fix bug in callback handling

This patch handles following-

- Don't create node handle and send to application
if Remote Node Discovery fails. Node Browsing
is mandatory command to discover remote node composition.
Without remote node composition, node handle
is meaningless. Therefore, send NULL in node handle
incase Node Browsing fails.

- Send Node feature information only when remote node feature
command is successful.

Change-Id: I85c78c89a22cf50cccb321f8d3d7fbeaee20a6ef
Signed-off-by: Anupam Roy <anupam.r@samsung.com>