We already had a path on the web client server struct, but hadn't
plumbed it through to the CLI. Add that now and use it for Synology and
QNAP instead of hard-coding the path. (Adding flag for QNAP is
tailscale/tailscale-qpkg#112) This will allow supporting other
environments (like unraid) without additional changes to the client/web
package.
Also fix a small bug in unraid handling to only include the csrf token
on POST requests.
Updates tailscale/corp#13775
Signed-off-by: Will Norris <will@tailscale.com>
