Galera: Add method to abort long-running SST

When a long-running SST is active the whole cluster will be blocked from performing other resource actions until the SST completes.

Would be great if we had an option to abort SST (and mark the resource on this node as failed), so other cluster operations can continue until the failcount is reset.

Maybe in the SST loop a check could be added if mysql is banned from the current node, so 'pcs resource ban galera nodeX' could be used to abort SST.

Locate the Galera resource agent's SST loop and review how it handles node bans and resource failure. Check how `pcs resource ban galera nodeX` is represented, then define completion as aborting the active SST, marking the resource failed on that node, and allowing other cluster operations to continue until the failcount is reset.

Written by the indexing model from the issue text.