qemuxml2argvtest: Remove pointless tests for keywrapping on s390
qemuxml2argvtest: Remove pointless tests for keywrapping on s390

There were two negative tests for the keywrapping feature on s390 when
the feature flag was missing. For now both shared the error message thus
worked fine, but with the upcoming patch to move some disk validation
code from the command line formatter to validation code will change the
error message in case the disk capabilities are missing.

Drop the test cases which don't provide any capability and keep those
that have the disk capabilities present as they are sufficient to prove
the feature.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Reviewed-by: Pavel Hrdina <d4772d05997b8abf035041e3b4f4996380ea7e7a@redhat.com>

nertpinx/libvirt,libvirt/libvirt,zippy2/libvirt,crobinso/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,crobinso/libvirt,nertpinx/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,zippy2/libvirt,zippy2/libvirt,olafhering/libvirt,crobinso/libvirt,jfehlig/libvirt,crobinso/libvirt,zippy2/libvirt,olafhering/libvirt