Allow variables on "Fail build threshold" field

Issue Summary

Currently Bamboo allows the creation and use of Plan variables. However, when using the Build warnings parser, it's possible to use the variable only when adding conditions to the task.

Steps to reproduce

1. Create a Plan
2. Create a plan variable
3. Create a Job
4. Create a task using Build warnings parser
5. Check the condition box of the task in order to use the Plan variable
6. Check the Fail build if too many warnings are found box
7. Add a value to the Fail build threshold field

Actual results

Possible to use the variable only when adding conditions to the task.

Expected results

Allow the use of variables on the Fail build threshold field:

Example

There is a solution that produces 1000 warnings but needs to configure the build to fail if the number of the warnings increases, but does not decrease.
And if the number decreases, use this new number as a threshold.

Initial value of the variable: 1000.

• Build #1 produces 1000 warnings – OK
• Build #2 produces 999 warnings – OK, and the variable values change to 999
• Build #3 produces 1000 warnings – FAIL because the current threshold is 999.
• Build #4 produces 500 warnings – OK, and the variable values change to 500