This means it now has three states, `true`, `false`, & `nil`. The
default state is now `nil` which does nothing instead of `false` which
now will explicitly disable ENA support instead of just not enabling it.
Run now takes a context as well as a statebag. We'll assign the context
to the blank identifier to prevent namespace collisions. We'll let the
step authors opt-in to using the context.
`find . -iname "step_*.go" -exec gsed -i'' 's/func \(.*\)Run(/func \1Run(_ context.Context, /' {} \;`
Set SriovNetSupport to "simple". As of February 2017, this applies to C3, C4,
D2, I2, R3, and M4 (excluding m4.16xlarge).
Set EnaSupport to true. As of February 2017, this applies to C5, I3, P2, R4,
X1, and m4.16xlarge.