Cleaner use of session in install script (#3276)
Cleaner use of session in install script (#3276)

Fix warning about session already started during install.
Refactor more code to use the same approach than in main FreshRSS.
Did not address all read accesses (not important) but did cover all
write accesses (important)
marienfressinaud/FreshRSS,Alkarex/FreshRSS,Alkarex/FreshRSS,FreshRSS/FreshRSS,aledeg/FreshRSS,FreshRSS/FreshRSS,marienfressinaud/FreshRSS,aledeg/FreshRSS,FreshRSS/FreshRSS,aledeg/FreshRSS,Alkarex/FreshRSS,aledeg/FreshRSS,marienfressinaud/FreshRSS,marienfressinaud/FreshRSS,FreshRSS/FreshRSS,Alkarex/FreshRSS