Sysbox CI fails consistently on `kind-custom-net` test ...

The Sysbox CI (Travis) is currently failing on the following test, due to a test env issue.

Executing tests/kind/kind-custom-net.bats ... 
1..6
not ok 1 kind custom net cluster up
# (from function `kindbox_cluster_setup' in file tests/kind/../helpers/k8s.bash, line 623,
#  in test file tests/kind/kind-custom-net.bats, line 58)
#   `kindbox_cluster_setup $cluster $num_workers $net $node_image $k8s_version' failed
not ok 2 kind deployment
# (in test file tests/kind/kind-custom-net.bats, line 73)
#   `[ "$status" -eq 0 ]' failed
# status = 1
# output = W0416 00:12:53.011575  305857 loader.go:223] Config not found: /root/.kube/cluster-config
# error: failed to create deployment: Post "http://localhost:8080/apis/apps/v1/namespaces/default/deployments?fieldManager=kubectl-create": dial tcp [::1]:8080: connect: connection refused
# kubeconfig = /root/.kube/cluster-config
not ok 3 kind service clusterIP
# (in test file tests/kind/kind-custom-net.bats, line 103)
#   `[ "$status" -eq 0 ]' failed
not ok 4 kind service nodePort
# (in test file tests/kind/kind-custom-net.bats, line 172)
#   `[ "$status" -eq 0 ]' failed
# cat: /tmp/k8s-test//.cluster_num_workers: No such file or directory
not ok 5 kind DNS clusterIP
# (in test file tests/kind/kind-custom-net.bats, line 241)
#   `[ "$status" -eq 0 ]' failed
not ok 6 kind custom net cluster down
# (from function `kindbox_cluster_teardown' in file tests/kind/../helpers/k8s.bash, line 646,
#  in test file tests/kind/kind-custom-net.bats, line 326)
#   `kindbox_cluster_teardown $cluster $net' failed
# cat: /tmp/k8s-test//.cluster_num_workers: No such file or directory
make: *** [Makefile:518: test-sysbox-local-ci] Error 1
make: *** [Makefile:375: test-sysbox-ci] Error 2
The command "make test-sysbox-ci" exited with 2.

The failure is 100% reproducible in the CI environment, though it's not reproducible in any of our local dev machines or other test machines. Thus, it's an issue that is specific to the Travis CI environment and we don't believe it's a bug in Sysbox.

Let's fix this ASAP so that we have a clean CI pipe in Sysbox-CE.