Skip EncryptionVolTypeTest in Iaas verification and CNTT Conformance

Skip EncryptionVolTypeTest in Iaas verification and CNTT Conformance

Attaching an encryted volume is optional in CNTT [1].

This test fails if the volume type already exists and if it runs
twice in parallel [2]. As this single test doesn't fullfil the Functest
requirements, it's skiped in the classical verification as well.

[1] https://github.com/cntt-n/CNTT/blob/master/doc/ref_arch/openstack/chapters/chapter05.md
[2] https://storyboard.openstack.org/#!/story/2007804

Change-Id: Ib6fc843d71704aab1bfc536133544eb3fa4f3e72
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>