Restore use of ENERGY_DATA in mageec-wand.exp.

The environment variable ENERGY_DATA used to control the placement of
the results file from the energytool script.  The last commit lost this
ability, this commit brings it back.

ChangeLog:

	* beebs.test/mageec-wand.exp (beebs_setup_before_all_benchmarks):
	Restore use of ENERGY_DATA environment variable to control path to
	output file.