MODULES-8947 fixing bugs and tests

[sheenaajay]

Request to review the following changes

• env settings specified for wait_for_default_sa & kube_addons.pp to set the env correctly
• upgraded the k8 version and go version on spec_helper_acceptance tests
• Updated the k8 version in the testcase
• Added the variable ignore_preflight_errors to init.pp
• updated the default value for etcd version
• coredns is default dns (hence modified the testcase for 1.13.5)

K8 Acceptance test Results
`he Kubernetes module
clean up before each test
kubernetes class
it should install the module and run
localhost $ scp /var/folders/4v/p90k7dqd65348jw6l6xrppdw0000gq/T/beaker20190425-35875-1puinxd ubuntu-1604-master:/tmp/apply_manifest.pp.dmlBKw {:ignore => }
should run
should install kubectl
should install kube-dns
application deployment
can deploy an application into a namespace and expose it
can access the deployed service
can delete a deployment

Finished in 26 minutes 14 seconds (files took 37.42 seconds to load)
6 examples, 0 failures`