Stop changing UseEntryGuards in authority and Tor2web configs
Instead, change a copy of the option's value. Introduced in commits 51fc6799 in tor-0.1.1.16-rc and acda1735 in tor-0.2.4.3-alpha.
Also, check the consistency of UseEntryGuards and EntryNodes after we change UseEntryGuards. Introduced in commit 686aaa5c in tor-0.2.4.12-alpha.
Part of #17178 (moved).