Update p4tc's iproute2 to v17-rc8

[fruffy]

Opening on behalf of @vbnogueira.

Fixes #5171 temporarily.

[jafingerhut]

@vbnogueira If you approve of these changes, please say so in a comment.

@ChrisDodd @vlstill If one or both of you can also approve (or suggest someone else to review it that can approve), I can go ahead and merge this. I say that not because I understand the details of the changes, but because it is passing all CI tests, which is a clear improvement over the current state of affairs. I am assuming that if any further related changes are desired, hopefully they will only affect the p4tc backend tests, not the other backend tests.

[ChrisDodd]

Looks like it should not affect anything non-tc related

[vlstill]

Looks safe for the rest of the compiler to me.

[jafingerhut]

Given that this is blocking everyone's p4c CI testing, I am going to merge this given Chris Dodd's review, and the fact that it is passing all CI tests. If there are problems that result from this merging, they are on my head, but I'm thinking positively right now :-)