GM doesn't require clock class check via PMC since GM manages the ClockClass

Addressing two problems
1. update clock class method which are called as a goroutine ; since go routines doesn't guarantee order of execution . This could result in multiple attempts to update clock class via PMC
2. T-GM do not need periodic Clock Class check since GM manages Clock Class and announcement .
Also with latest version of linuxPTP we can subscribe to ClockClass Events for non T-GM; which will get rid of PMC call to verify clock class every 5 sec 

Implementation Idea to avoid Go-routine for passing jobs to update clock class.
either using channel or mutex