LbPlatformUtils.host_supports_tag should not restrict to released platforms
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LbPlatformUtils.host_supports_tag, used by lb-run to know is a binary tag is usable on the host, compares the tag with the list of tags from lb-describe-platform which only contains the tags used for a release.
While this is find in something like LHCbDIRAC, it's very unpractical when we need to test new platforms from the nightly builds.
The correct behaviour should be to delegate to LbPlatformUtils.can_run.
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