solaris and illumos use PeerCreds too

Per tailscale/peercred#10

Signed-off-by: Nahum Shalman <nahamu@gmail.com>

ipn/ipnserver/actor.go

@@ -237,7 +237,7 @@ func connIsLocalAdmin(logf logger.Logf, ci *ipnauth.ConnIdentity, operatorUID st
 		// This is a standalone tailscaled setup, use the same logic as on
 		// Linux.
 		fallthrough
-	case "linux":
+	case "linux", "solaris", "illumos":
 		if !buildfeatures.HasUnixSocketIdentity {
 			// Everybody is an admin if support for unix socket identities
 			// is omitted for the build.

safesocket/safesocket.go

@@ -120,7 +120,7 @@ func PlatformUsesPeerCreds() bool {
 // runtime.GOOS value instead of using the current one.
 func GOOSUsesPeerCreds(goos string) bool {
 	switch goos {
-	case "linux", "darwin", "freebsd":
+	case "linux", "darwin", "freebsd", "solaris", "illumos":
 		return true
 	}
 	return false