unionfs7.sh: eliminate stderr redirection

[jah]

Summary

The bash-ism here results in an "ambiguous output redirect"
error when run under tcsh. Similar unionfs stress2 tests don't
do this, and unionfs7 doesn't seem to generate spurious output
when run locally, so just delete it.

[pho]

Looks good to me.

[pho]

PS
Feel free to fix or add any unionfs tests you like.