[hbase-operator-tools] Extra checks on RegionsMerger to avoid submitting merge requests for regions with merge qualifiers

When iterating over existing region over cycles to perform merges, RegionsMerger may try to merge two regions that had been recently merged and would then have still have a "merge" qualifier to sign these still refers to parent regions files. That means the request is useless, the created SCPs would be aborted right away once it finds the so called merge qualifiers. RegionsMerger should avoid submitting these attempts, by checking for merge qualifiers and skipping those that still have merge qualifiers.