mesh: Heartbeat fixes for message count
mesh: Heartbeat fixes for message count

Both count and period must be non-zero for message publication
Stop publication when count becomes zero
Add count to debug message in hb_publish

Ported from Zephyr PR #4354

X-Original-Commit: 03d343d1147eca07c123e787b1368bf5234f64c5

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