Fix for getting optional information about openshift cluster version.

[ratsuf]

Description

In the case of openshift distribution, there is an invocation of kubectl get clusterversion. But such a type of resource not present in OKD 3.11 and lower. As a result - #133
Because the result of 'clusterversion' used just for reference in the logs, I suggest the following fixes:

Fixes

1. Added optional_invoke method because current invoke stops Cerberus execution with UnboundLocalError in case of exception.
2. Used the optional invoke method for collecting reference information about openshift cluster.

[comet-perf-ci]

Can one of the admins verify this patch?

[seanogor]

LGTM

[amitsagtani97]

/rerun all

[comet-perf-ci]

Test	Result	Duration
test_daemon_disabled	Pass	00:00:29
test_detailed_data_inspection	Pass	00:00:54
test_slack_integration	Pass	00:01:06

Check	Gold time (s)	PR time (s)	% Change
"check_master_taint"	.180727	.187929	3.98
"entire_iteration"	3.587589	3.354181	-6.50
"sleep_tracker"	1.280952	1.192856	-6.87
"watch_cluster_operators"	.522088	.518089	-.76
"watch_csrs"	.128074	.128175	.07
"watch_namespaces"	1.312096	1.195382	-8.89
"watch_nodes"	.252358	.242000	-4.10

[paigerube14]

The CI needs to be updated to be 120 characters not 110. Will be fixed in PR

LGTM

[chaitanyaenr]

@ratsuf we might want to rebase the PR.

[ratsuf]

@chaitanyaenr I've rebased the PR.

[ratsuf]

@chaitanyaenr should I change something else?

[chaitanyaenr]

/rerun all

[chaitanyaenr]

LGTM

[comet-perf-ci]

Test	Result	Duration
test_daemon_disabled	Pass	00:00:29
test_detailed_data_inspection	Pass	00:00:51
test_slack_integration	Pass	00:01:04

Check	Gold time (s)	PR time (s)	% Change
"check_master_taint"	.185639	.200576	8.04
"entire_iteration"	3.370921	3.446879	2.25
"sleep_tracker"	1.204920	1.221290	1.35
"watch_cluster_operators"	.513252	.527975	2.86
"watch_csrs"	.126635	.127082	.35
"watch_namespaces"	1.206616	1.226955	1.68
"watch_nodes"	.232474	.228316	-1.78