jets that bail with %exit get ice set to c3y

[mrdomino]

Describe the bug
Equivalence testing is currently implemented as follows:

1. Check _(ham_u->ice).
2. If c3n, then set ham_u->ice = c3y.
3. Run ham_u->fun_f.
4. Set ham_u->ice = c3n.

However, if ham_u->fun_f returns u3m_bail(c3__exit) (as commonly happens in jet code), then:

1. no diagnostic is printed indicating that the call bailed.
2. ham_u->ice is never reset to c3n.
3. Future calls will therefore treat the jet as though it was perfect.

To Reproduce
Steps to reproduce the behaviour:

1. Set a jet’s .ice to c3n.
2. Have the jet body return u3m_bail(c3__exit).
3. Observe (e.g. through printfs / ~&) that the hoon code is not called after the first bail, and the C code is called.

Screenshots
If applicable, add screenshots to help explain your problem.

System (please supply the following information, if relevant):

• Vere 1.9rc1

Notify maintainers
@joemfb @frodwith

[joemfb]

This behavior is fine for equivalence testing in local development, but obviously not suitable for livenet-deployed testing. This was known, just not to me -- moar and better testing remains highly desirable.