qa: ensure deterministic mem.numa.max_bandwidth values in 821
qa: ensure deterministic mem.numa.max_bandwidth values in 821

Test 821 is susceptible to a pre-existing bandwidth.conf file
interfering with the output of the test.  If that file exists,
stash it away at the start and re-instate at the tests end.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp