Revert "build_debs: horrible hack to remove libbabeltrace from wheezy build deps"

This reverts commit 40a6547fbd2260b4d2e3277242fe97348a826cb9.

This doesn't work.
move wheezy hack into build_dsc.sh, where it belongs

Signed-off-by: Sage Weil <sage@redhat.com>