mesh: Take advantage of K_SECONDS macro
mesh: Take advantage of K_SECONDS macro

This makes the code slightly more readable.

X-Original-Commit: e7c0eeb1e909c17794af5c2d59efcd729385dd7b

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