owncloud: Make setup more robust to repeatition
owncloud: Make setup more robust to repeatition

Create postgresql user and set password in two steps instead of one.  This
ensures that if a user already exists for some reason (setup already run), then
re-running will simply set a new password and generates a new configuration.
Otherwise, the user creation setup having failed because of existing user will
also fail to set new password and the generated configuration is not usable.

jvalleroy/plinth-debian,vignanl/Plinth,freedomboxtwh/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,kkampardi/Plinth,kkampardi/Plinth,freedomboxtwh/Plinth,vignanl/Plinth,jvalleroy/plinth-debian,harry-7/Plinth,freedomboxtwh/Plinth,jvalleroy/plinth-debian,vignanl/Plinth,harry-7/Plinth,kkampardi/Plinth,kkampardi/Plinth,vignanl/Plinth,harry-7/Plinth,vignanl/Plinth,harry-7/Plinth,jvalleroy/plinth-debian,harry-7/Plinth,freedomboxtwh/Plinth,jvalleroy/plinth-debian