Added SIGTERM signal handling for graceful shutdown of Litmus-Checker #344

Job	Run time
shell-checker	7s
changes	6s
litmus-checker	1m 20s
litmus-app-deployer	0s
litmus-qps-cmd	0s
litmus-infra-hardened-alpine	0s
cassandra-client	0s
kafka-client	0s
litmus-curl	0s
litmus-experiment-hardened-alpine	0s
litmus-git-app-checker	0s
litmus-k8s	0s
litmus-argocli	0s
kafka-deployer	0s
litmus-argo-workflow-controller	0s
litmus-argo-workflow-executor	0s
mongo	0s
tpcc-client	0s
mysql-client	0s
sysbench-client	0s
dd-client	0s
custom-client	0s
logger	0s
memleak	0s
mongo-client	0s
postgres-client	0s
stress-ng	0s
container-killer	0s
elasticsearch-stress	0s
fio	0s
forkbomb	0s
memory-stress	0s
nfs-client	0s
litmusctl	0s
litmus-helm-agent	0s
litmus-pg-jmeter	0s
litmus-pg-load	0s
litmus-redis-load	0s
mongo-utils	0s
	1m 33s

Provide feedback