(#22322) Suppress swap stderr on AIX and Solaris

When `swap -l` is run on Solaris and no swap devices are present,
the command emits "No swap devices configured". This commit squelches
the stderr output to reduce the noice produced when running Facter.

This supersedes GH-530.
Merge branch 'issue/22322-suppress_swap_stderr_output' into stable
Merge branch 'stable'

Conflicts:
	spec/unit/memory_spec.rb