Fix SocketFlags usage on AIX #729

Job	Run time
windows_gnu (nightly, x86_64-pc-windows-gnu)	1m 15s
msrv (ubuntu-latest)	1m 45s
msrv (windows-latest)	1m 44s
cross (ubuntu-latest)	1m 41s
clippy	26s
fmt	9s
cross (macos-latest)	31s
security_audit	5s
test (ubuntu-latest, nightly)	47s
test (ubuntu-latest, beta)	41s
test (ubuntu-latest, stable)	40s
test (windows-latest, nightly)	1m 17s
test (windows-latest, beta)	1m 6s
test (windows-latest, stable)	1m 18s
test (macos-latest, nightly)	1m 11s
test (macos-latest, beta)	1m 0s
test (macos-latest, stable)	46s
	16m 22s

Provide feedback