tweak phpunit-junit macros

The 'phpunit-junit' builder and publisher macros are now both logging to
'log/junit-phpunit.xml', the 'log' dir being created.

Updated operations-mw-config-tests to use them instead of a specific
shell.

Change-Id: Ib8c0b119b76a5a42aaace932da119c4492063d2e