The

  del profile.test_list[key]

statement was silently failing because the TestDict's key lowering magic
was not happening for deleted items.

Unfortunately this still is not enough to fix the glean exclusions:
somehow all glean test names are being munged with extra whitespace.
For example:

  $ ./piglit-print-commands.py tests/llvmpipe.py | grep '^glean/p'
  warning: test glean/pointAtten does not exist
  warning: test glean/texCombine does not exist
  [...]
  glean/p o i n t a t t e n ::: bin/glean -o -v -v -v -t +pointAtten --quick

Reviewed-by: Dylan Baker <baker.dylan.c@gmail.com>