tests: lcitool: Switch to OpenSUSE Leap 15.4

tests: lcitool: Switch to OpenSUSE Leap 15.4

Since OpenSUSE Leap 15 counts as a single major release of an LTS distribution,
lcitool has changed the target name to remove the minor version.  Adjust the
mappings and refresh script.

This also updates the dockerfile to 15.4, since the 15.3 version is EOL now:

https://get.opensuse.org/leap/15.3

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <a408b7f241ac59e5944db6ae2360a792305c36e0.1681735482.git.pkrempa@redhat.com>
[Adjust for target name change and reword commit message. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>