make sure only one upgrade process is active at any time (kind of)
make sure only one upgrade process is active at any time (kind of)

samtuke/phplist3,bramley/phplist3,samtuke/phplist3,samtuke/phplist3,phpList/phplist3,bramley/phplist3,phpList/phplist3,mariez/phplist3,phpList/phplist3,danwaterloo/phplist3,samtuke/phplist3,phpList/phplist3,mariez/phplist3,mariez/phplist3,mariez/phplist3,danwaterloo/phplist3,mariez/phplist3,danwaterloo/phplist3,bramley/phplist3,danwaterloo/phplist3,bramley/phplist3,danwaterloo/phplist3,samtuke/phplist3,phpList/phplist3,bramley/phplist3