Fix #4246 - More undef 'payload_exe' in other modules

Root cause: payload_exe is an accessor in the TFPT command stager
mixin, you need stager_instance in order to retreive that info.
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Fix #4246

... so it will automatically close the ticket.
Clarify about how BES uses os_flavor

We don't. We don't use os_flavor anymore because it is no longer
implemented. We get the information from os_name instead.
Fix rspec
No mercy for os_flavor
Fix description
Add Portuguese target, lands #3961 (also reorders targets)
Land #4384, fix typo.
Land #4343, os_flavor reduction
Land #4324, payload_exe rightening.

Fixes #4323, but /not/ #4246.
Merge code in from #2395
Deconflicts and lands #2395, a rework of persistence