net: TestLookupPort_Minimal and TestResolveTCPAddr fail on android/386

[eliasnaur]

From https://build.golang.org/log/4f1d81143e54a9337acc5d6e6ab240be55f55ecf

--- FAIL: TestLookupPort_Minimal (0.00s)
	lookup_test.go:693: LookupPort("tcp", "http") = 0, lookup tcp/http: servname not supported for ai_socktype; want 80, error=nil
	lookup_test.go:693: LookupPort("tcp", "HTTP") = 0, lookup tcp/HTTP: servname not supported for ai_socktype; want 80, error=nil
	lookup_test.go:693: LookupPort("tcp4", "http") = 0, lookup tcp4/http: servname not supported for ai_socktype; want 80, error=nil
	lookup_test.go:693: LookupPort("tcp6", "http") = 0, lookup tcp6/http: servname not supported for ai_socktype; want 80, error=nil
--- FAIL: TestResolveTCPAddr (0.00s)
	tcpsock_test.go:334: ResolveTCPAddr("tcp", "127.0.0.1:http") = <nil>, lookup tcp/http: servname not supported for ai_socktype, want 127.0.0.1:80, <nil>
	tcpsock_test.go:334: ResolveTCPAddr("tcp", "[::ffff:127.0.0.1]:http") = <nil>, lookup tcp/http: servname not supported for ai_socktype, want 127.0.0.1:80, <nil>
	tcpsock_test.go:334: ResolveTCPAddr("tcp", "[2001:db8::1]:http") = <nil>, lookup tcp/http: servname not supported for ai_socktype, want [2001:db8::1]:80, <nil>
	tcpsock_test.go:334: ResolveTCPAddr("tcp4", "127.0.0.1:http") = <nil>, lookup tcp4/http: servname not supported for ai_socktype, want 127.0.0.1:80, <nil>
	tcpsock_test.go:334: ResolveTCPAddr("tcp4", "[::ffff:127.0.0.1]:http") = <nil>, lookup tcp4/http: servname not supported for ai_socktype, want 127.0.0.1:80, <nil>
	tcpsock_test.go:334: ResolveTCPAddr("tcp4", "[2001:db8::1]:http") = <nil>, lookup tcp4/http: servname not supported for ai_socktype, want <nil>, address 2001:db8::1: no suitable address found
	tcpsock_test.go:334: ResolveTCPAddr("tcp6", "127.0.0.1:http") = <nil>, lookup tcp6/http: servname not supported for ai_socktype, want <nil>, address 127.0.0.1: no suitable address found
	tcpsock_test.go:334: ResolveTCPAddr("tcp6", "[::ffff:127.0.0.1]:http") = <nil>, lookup tcp6/http: servname not supported for ai_socktype, want <nil>, address ::ffff:127.0.0.1: no suitable address found
	tcpsock_test.go:334: ResolveTCPAddr("tcp6", "[2001:db8::1]:http") = <nil>, lookup tcp6/http: servname not supported for ai_socktype, want [2001:db8::1]:80, <nil>
FAIL
exitcode=1go_android_exec: adb shell rm -rf /data/local/tmp/net.test-31630
FAIL	net	3.326s

It seems to be that the net package doesn't properly falls back to the Go "services" fallback in lookup.go, but I wasn't sure how to do it properly.

@bradfitz because he touched it last with https://go-review.googlesource.com/c/28951/ and with #17045.

[gopherbot]

CL https://golang.org/cl/34014 mentions this issue.