Don't close modals until backend returns

[mortengf]

Currently, the modals close before the backend returns, i.e. the modal is closed before the sweet alert is shown. This is confusing for the user.

• For upgrade, don't close the "payment" modal until the backend returns.
• For downgrade, don't close the "upgrade" modal until the backend returns.

[Abekonge]

Perhaps add out "processing gif" on the upgrade button until the sweet alert is shown as well?