Memory leak in simple_mesh_node

Problem Description:

About ~200 bytes of heap is lost every connection established when the simple_mesh_node project is configured for in the "Mesh and Peripheral". This eventually leads to an assert that crashes the customer's application when heap space runs out.

SDK version tested: 5.20

Setup:

1. In the simple_mesh_node project, change the Mesh Application to "Mesh and Peripheral".
2. Add HEAPMGR_METRICS to track the heapmgrMemFreeTotal while debugging
3. Record the heapmgrMemFreeTotal before entering a connection, then enter a connection with a smartphone.
4. Disconnect from the device and you will see that heapmgrMemFreeTotal is ~200 bytes smaller than prior to connection establishment.

Alternate setup using Out of box firmware:

1. Build and flash a default simple_mesh_node project.
2. Initialize the node to advertise unprovisioned beacons.
3. Using Lightblue, connect to the Simple mesh node and then disconnect, while recording the heapmgrMemFreeTotal. You should see the same behavior described above.

I have verified this on my end and observe ~200 bytes (200 bytes is not exact and varies for each connection/disconnection).