Clean-up to global overrides in NewParserTest

Clean-up to global overrides in NewParserTest

- Move definitions of constant values from NewParserTest::setupGlobals()
  to NewParserTest::setUp() so that the former only defines values
  depending on the test
- Remove duplicate definitions
- Use setMwGlobals() to override the globals in NewParserTest::setUp()
- Change the overriding of $wgNamespaceProtection to use the normal
  procedure instead of the "weirdglobal" thing
- Only define $wgUser, $wgOut and $wgRequest in NewParserTest::setupGlobals()

Change-Id: I1362932db2230455b23e469759ff3f9946da0392