Don't compare User-Agent in http_auth_offered test

[tcely]

I don't understand why User-Agent header is listed as part of valid.

I checked the commits and it seems like you're constantly updating the version strings shown in this header for libgit2 which is as far as I know not a version you control. It seems like this has nothing to do with the test and should just be removed from the valid headers list.

See: https://github.com/rust-lang/cargo/blob/0.26.0/tests/build-auth.rs#L23

Also, Accept doesn't seem to be under test here and doesn't change. I'm not sure why it should be in this list either.

[alexcrichton]

I believe this has since been fixed

[tcely]

It appears unchanged in the latest release.

https://github.com/rust-lang/cargo/blob/0.28.0/tests/testsuite/build_auth.rs#L20

[jirutka]

I believe this has since been fixed

Programming is not a religion!

It was not fixed, not in 0.28.0, nor in the current master, see tests/testsuite/build_auth.rs:20.