cmd/tailscale/cli: fix fixTailscaledConnectError for macsys version

Currently, on macOS Standalone version if local client returns any
errors while tailscaled is running, cli would not print the error at
all, showing only that Tailscale might not be running.

Add tailscaled process name of macsys version, so that
fixTailscaledConnectError reports error correctly.

Contains workaround for go-ps bug which trims long process names (>16
characters): mitchellh/go-ps#15

Signed-off-by: Ilya Lukyanov <il@joom.com>

cmd/tailscale/cli/diag.go

@@ -32,7 +32,8 @@ func fixTailscaledConnectError(origErr error) error {
 			foundProc = proc
 			break
 		}
-		if runtime.GOOS == "darwin" && base == "IPNExtension" {
+		// go-ps might trim process names to 16 chars, macsys tailscaled binary is named io.tailscale.ipn.macsys.network-extension
+		if runtime.GOOS == "darwin" && (base == "IPNExtension" || strings.HasPrefix(base, "io.tailscale.ipn")) {
 			foundProc = proc
 			break
 		}