Skip the aio_suspend test on Linux

On Travis (and only on Travis) this test crashes.  It hits an internal
assertion within glibc.  It happens reliably with rustc 1.37.0.  Ignore
the test until Travis updates its images; then we'll try again.

Issue #1099

Author: asomers

test/sys/test_aio.rs

@@ -133,6 +133,10 @@ fn test_fsync_error() {
 
 #[test]
 #[cfg_attr(all(target_env = "musl", target_arch = "x86_64"), ignore)]
+// On Travis, aio_suspend hits an assertion within glibc.  This is either a bug
+// in Travis's version of glibc or Linux.  Either way, we must skip the test.
+// https://github.com/nix-rust/nix/issues/1099
+#[cfg_attr(target_os = "linux", ignore)]
 fn test_aio_suspend() {
     const INITIAL: &[u8] = b"abcdef123456";
     const WBUF: &[u8] = b"CDEFG";