Check for updates of "additional software" only once

“Additional software” are checked for updates every time the network gets connected, which is rather annoying and pointless on a bad Wi-Fi network for example. i propose to have “additional software” checked for updates only once per working session: after the first connection to Tor.

Team: alan (code), sajolida (ux), kurono (reviewer), segfault (reviewer), u (maybe)

Feature Branch: bugfix/9059-additional-software-after-session greeter:bugfix/9059-additional-software-after-session

Related issues

Related to #9059 (closed)
Related to #5996 (closed)
Related to #14570 (closed)

Original created by @sajolida on 9819 (Redmine)

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