Fixing manual payout race condition

* Mark manual payout active
* Run payout logics
* Reset manual payout

This ensures only one manual transaction can be run at a time.
If any users starts a manual payout others have to wait until the site
completed loading and finished the transaction process.

As long as we don't have too many users doing a manual payout at the
same time this should not be an issue. Best for users is using auto
payouts anyway.

This addresses #149
Merge pull request #154 from TheSerapher/issue-149

Fixing manual payout race condition, fixes #149