summary.py: Adds a generatJUnit method to NewSummary

This new method leverages mako to generate JUnit xml rather than using
junit.py.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
piglit-summary-junit.py: Use NewSummary.generateJUnit

Stop using the old JUnit generation code, and start using the new code.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
junit.py: Remove unused file

Since this is no longer in use, remove it

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