Prior to this change, any `MapPropertySource` created by an `EnvironmentPostProcessor` would be processed by `BootstrapApplicationListener`. If that property source had a conditional property that it created itself, the 2nd run (bootstrap causes EPPs to run twice) would not have the property and that property source would end up in the main `Environment` effectively deleting a property.
This change only deals with `MapPropertySource`s created by boot testing for a specific sub-type.
Fixes gh-476
109e5779e9