Disallow 'timeout' in health_monitor to be negative

It should limit the value of 'timeout' in 'health_monitor', the 'timeout'
shouldn't to be negative.

Change-Id: I26ae1995c9cc362df7c7dda4c53fb8adda298d13
Closes-bug: #1320062
Merge "Disallow 'timeout' in health_monitor to be negative"