reactor: reinstate aio-nowait support
reactor: reinstate aio-nowait support

Nowait-aio was disabled in e67572ef68a6cd1f0785d1f19f5ab8e18816763b, but was
since fixed in the kernel (in 5.1). Whitelist all kernels known to contain the
fix.

syuu1228/seastar,avikivity/seastar,avikivity/seastar,syuu1228/seastar,dreamsxin/seastar,cloudius-systems/seastar,dreamsxin/seastar,cloudius-systems/seastar,scylladb/seastar,scylladb/seastar,dreamsxin/seastar,cloudius-systems/seastar,avikivity/seastar,syuu1228/seastar,scylladb/seastar