runtime: restore "goroutine in C code" message
In the 1.9 upgrade I took out the word "goroutine" from a traceback
showing a goroutine running in C code, to let TestCgoNumGoroutine
pass. However, it turns out that some code is actually checking for
that string; for example,
https://github.com/grpc/grpc-go/blob/master/test/leakcheck/leakcheck.go#L44
So keep the message the same, and change the test.
Reviewed-on: https://go-review.googlesource.com/64850
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@252991 138bc75d-0d04-0410-961f-82ee72b054a4