Update create date of bounty only once.

[ecurrencyhodler]

Describe the bug
Superadmin is displaying incorrect bounties. The query of the date range should account for bounty creation date. But instead it's showing something different. Possible latest activity.

Here is an example. I set a custom date range from 9/9-9/15 and saw this bounty:
https://community.sphinx.chat/bounty/1302

When I click the bounty it also shows the creation date as "a day".

But I posted this bounty 1/29

Upon further investigation, the problem is that the field "created" gets updated whenever a bounty gets saved.

Expected behavior
Creation date of bounties should reflect the date it was created only. The "created" field should only get updated once, which is when a bounty gets created.

Desktop (please complete the following information):

• Browser: Chrome

Acceptance Criteria

• I have tested on Chrome desktop
• I have rebased and tested locally before submitting my PR
• I can submit a PR within 2 days of taking the bounty

Here is an example backend test

[ecurrencyhodler]

@elraphty can you take a look at this issue when you get a chance? Let's find the cause and see what is needed to fix then make some bounties.

[ColdMice]

@ecurrencyhodler would this be available to work on? or this is reserved?

[wright-eric]

Assign

[ecurrencyhodler]

Sorry just missed your comment cold mice.