iotests: Test 183 does not work on macOS and OpenBSD

In the long run, we might want to add test 183 to the "auto" group
(but it still fails occasionally, so we cannot do that yet). However,
when running 183 in Cirrus-CI on macOS, or with our vm-build-openbsd
target, it currently always fails with an "Timeout waiting for return
on handle 0" error.

Let's mark it as supported only on systems where the test is working
most of the time (i.e. Linux, FreeBSD and NetBSD).
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>
Message-id: 20200121095205.26323-4-thuth@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

tests/qemu-iotests/183

@@ -42,6 +42,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.filter
 . ./common.qemu
 
+_supported_os Linux FreeBSD NetBSD
 _supported_fmt qcow2 raw qed quorum
 _supported_proto file