HDFS-WriterApp-Fixed all the code review comments

HDFS-WriterApp-Fixed all the code review comments

Fixed all the code review comments by Kiran

	1. Implemented a boolean channel instead of empty struct channel for signal, use WaitGroup
	to ensure all writers finish cleanup.
	2. Introduce JSON tags for configs
	4. remove all panic and fatalf code to ensure that the app doesnt crash anytime.
	5. remove unneccessary hdfsWriter null checks.
        6.remove the 'run' variable used in the infinite loop, replaced with 'return'

Issue-ID: ONAPARC-453
Change-Id: Ic77c59dc75a8898a3cf34999850e6687d40e7faa
Signed-off-by: Rajamohan Raj <rajamohan.raj@intel.com>