add psp support when its configured in acceptance tests

[kschoche]

Changes proposed in this PR:

• Adds PSP support global.psp.enable=true to vault when it is enabled in nightly acceptance tests. currenlty the GKE-1.19 nightly is failing due to missing PSP in vault installation.

How I've tested this PR:
deployed with this flag on a local cluster and saw that it created the PSP policies:

demo $ k get psp
Warning: policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
NAME                               PRIV    CAPS   SELINUX    RUNASUSER          FSGROUP     SUPGROUP    READONLYROOTFS   VOLUMES
test-fztisb-vault                  false          RunAsAny   MustRunAsNonRoot   MustRunAs   MustRunAs   false            configMap,emptyDir,projected,secret,downwardAPI,persistentVolumeClaim
test-fztisb-vault-agent-injector   false          RunAsAny   MustRunAsNonRoot   MustRunAs   MustRunAs   false            configMap,emptyDir,projected,secret,downwardAPI

How I expect reviewers to test this PR:
code review

Checklist:

• Tests added
• CHANGELOG entry added

  HashiCorp engineers only, community PRs should not add a changelog entry.
  Entries should use present tense (e.g. Add support for...)