mesh: Check Heartbeat Pub count prior scheduling delayed work
mesh: Check Heartbeat Pub count prior scheduling delayed work

This check is needed to not schedule the delayed work if current
message to be sent is the last heartbeat message.

X-Original-Commit: 038539819e166b891355277c15e563dce2df959c

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble