Previously were always setting `UseSocketOnly` because we were
comparing `args.socketpath != ""`, but `args.socketpath` flag
always gets filled with `paths.DefaultTailscaledSocket()` when
not provided. Rather than comparing to the empty string, compare
to the default value to determine if `UseSocketOnly` should be
set.
Should fix issue with web client being unreachable for Mac App
Store variant of the mac build.
Updates #16054
Signed-off-by: Sonia Appasamy <sonia@tailscale.com>
c2fe123232