[DSEC-963] add retry loop

[sarahgibs]

Several small pipeline changes to try and improve reliability.
A new retry loop around creating an engagement in defect dojo. Several scans were consistently failing on this step, and hopefully this helps to alleviate this issue.
Broke out the zap shutdown action, and tried to fix the intermittent timeout issue.

The TIMEOUT_MINS value was increased by one. This value is used for communicating with the local instance of ZAP. There had been an increase in timeouts when connecting with ZAP from the zap-scans controller, and this is an attempt to reduce those timeouts.

The requestspersecond value was decreased by 1. This is across all scans as an attempt to reduce issues where the scanner was encountering 502 or 503 errors while scanning.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[TomConner]

Looks good - retry for dojo connections and for zap shutdown.

I notice you also increased a Hail timeout - perhaps add a comment about that in the PR conversation (if not split to a separate PR).