Feature: Add an optional argument to the alua prioritizer, "exclusive_pref_bit". If this argument is added, and a path has the TPGS pref bit set. Multipath will make a pathgroup using only that path, and assign it the highest priority
Reason: Some users want to use the TPGS pref bit to specify a single path that multipath should prefer to use. This was previously done. However, and change to how the prioritizers worked make this no longer happen. This option restores the ability for those who need it.
Result: Users can now either allow the preferred path to be in a path group with other paths that are equally optimized (the default) or in a path group by itself (by adding the exclusive_pref_bit argument)