Tweak test priorities back in sync with wiki / criteria
    
    The rule for test priorities is pretty simple. Ranges of
    priority values map to the 'Milestone' by which the test must
    be passing, per the release criteria. The priority for each
    openQA test is the *highest* priority for any wiki test case /
    criterion it covers.
    
    0-20: critical smoke tests (higher than Alpha priority)
    20-29: Alpha priority
    30-39: Beta priority
    40-49: Final priority
    50+: Optional priority
    
    Note that tests for non-release-blocking arches or images must
    always be over 50; I've simply added 50 to the values for all
    i386 tests in this change. Other than that, I just corrected a
    few values which had got out of whack or were originally set
    wrong.