Redirect is cached by browser

[altergui]

I just stumbled upon this behaviour using chromium Version 73.0.3683.75 (Developer Build) built on Debian 9.8, running on Debian 9.4 (64-bit)
connected to a libremesh running

root@LiMe-e9b944:~# opkg list *pirania*
pirania - 2019-09-27-1569563798
pirania-app - 2019-09-27-1569563798
shared-state-pirania - 2019-09-27-1569563798

browsed to http://ip4.me/
i was redirected to captive portal (thisnode.info/portal), entered a valid voucher and got internet access.
opened a new tab, and tried to browse to http://ip4.me/, i was again redirected to thisnode.info/portal. retried many times, every time i got redirected.
(i tried on a new browser session, and i was not redirected)
i did not look further into it but i got the impression that the browser is caching the redirect, which could be because pirania is sending "301 moved permanently" (permanent redirect) instead of "302 moved temporarily". is this the case? if then, i suggest to change it to 302

[luandro]

Seems the same as #47. It's set to 302 (https://github.com/libremesh/pirania/blob/master/pirania/files/www/pirania-redirect/redirect#L12)