Fix default TTL for AWS secrets

[joelthompson]

The default TTL was being offered as 30 minutes, and when unchanged, the
UI wouldn't send the TTL back to the backend, causing it to use the
default of 60m. Fix the TTL to default back to 1 hour.

[joelthompson]

I've left the default set to 3600s because that's how it's specified in the backend code. However, even if I specify it as 60m (a little more friendly for people to think about), it always seems to display 3600s anyway... not sure if there's a way to always display it in a more friendly format.

[joelthompson]

Also, @meirish -- one other note on this -- this is just a temporary patch. I'm proposing changing the default on a per-role basis in #5138, and so the same type of thing I mentioned in #5193 (comment) (i.e., read the role data and update the UI based on the role data) might need to be done here, though we could also just get away with a "role-default" selection instead of having a real TTL specified.

[meirish]

Looks good!

Yeah currently it will always show values from the server in seconds, we have a TODO to make this better.

Agreed about reading the role data first (if a user has access) to make the generate form better - this is something I thought of when finishing this up, but didn't have time to look into. It could make the whole experience much nicer.

[joelthompson]

If there's some quick guidance you can provide me about how to read the role data first, I could try to take a stab at it, but I don't really know where to start.