cmd/trace: TestGoroutineInSyscall flaky on the solaris-amd64 builder

[mvdan]

I see four failures on the first page of build.golang.org:

https://build.golang.org/log/eeeeb3f1845acf9a7d7fa7383c493043131115ac
https://build.golang.org/log/bb41faf383730d8675194a44c4bd41c4fc64676b
https://build.golang.org/log/0460aefacae9391ac02b6537002436051b2cad61
https://build.golang.org/log/d01e6073f52fc2d647b7e9fae6e949b4dd0b6cf1

/cc @hyangah @aclements

[gopherbot]

Change https://golang.org/cl/105821 mentions this issue: cmd/trace: skip GoroutineInSyscall in case time order err