Add options to support TLS certificate verification

Add --os-cacert and --verify|--insecure options using the same
sematics as the other project CLIs.  --verify is included for
completeness.

Bug: 1236608

Change-Id: I8a116d790db5aa4cb17a2207efedce7cb229eba3
Merge branch 'test-clientmanager' into dt-test