issue561 STF tests failing

[hackedy]

I'd expect these failures are related. Both tests expect some bits of the packet to be high but get all zeroes instead.

[hackedy]

This includes all the issue561 tests:

• [ ] issue561-1-bmv2.p4
• [ ] issue561-2-bmv2.p4
• [ ] issue561-3-bmv2.p4
• [ ] issue561-4-bmv2.p4
• [ ] issue561-5-bmv2.p4
• [ ] issue561-6-bmv2.p4
• [ ] issue561-7-bmv2.p4