Add "k3s certificate check" clause for better test coverage #1784

Job	Run time
Build Go Tests	56s
build / Build	6m 53s
E2E Tests (startup)	11m 24s
Docker Tests In GO (basics)	59s
E2E Tests (s3)	8m 30s
Docker Tests In GO (bootstraptoken)	1m 4s
E2E Tests (btrfs)	4m 50s
Docker Tests In GO (cacerts)	52s
Docker Tests (basics)	1m 5s
E2E Tests (externalip)	4m 28s
Docker Tests In GO (etcd)	2m 10s
Docker Tests (bootstraptoken)	54s
E2E Tests (privateregistry)	5m 54s
Docker Tests (cacerts)	46s
Docker Tests In GO (lazypull)	1m 10s
E2E Tests (embeddedmirror)	5m 42s
Docker Tests (compat)	2m 27s
Docker Tests In GO (skew)	1m 42s
E2E Tests (wasm)	4m 16s
Docker Tests (lazypull)	57s
Docker Tests In GO (upgrade)	1m 34s
Docker Tests (upgrade)	2m 15s
	1h 10m 48s

Provide feedback