Missing `def` keyword in groovy

Noticed the following warning messages in the [Jenkins job](https://hyc-runtimes-jenkins.swg-devops.com/job/Grinder_JCK/3864/console).

```
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named SPEC (to a value of type String) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named dockerAgents (to a value of type ArrayList) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named dockerAgentLabel (to a value of type String) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named LABEL (to a value of type String) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named LABEL (to a value of type String) which could lead to memory leaks or other issues.
...
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named dynamicAgents (to a value of type ArrayList) which could lead to memory leaks or other issues.
```

The linked Jenkins job console is the starting entry point; search the aqa-tests Groovy pipeline for assignments to SPEC, dockerAgents, dockerAgentLabel, LABEL, and dynamicAgents. Confirm the relevant assignments no longer produce the reported warnings in that job's console.

Written by the indexing model from the issue text.