Jenkins Style Checks (EOL Check, Tab Check, Copyright Check) running under task for incorrect branch

[dilijev]

See checks that ran for #2826, in particular: https://ci.dot.net/job/Microsoft_ChakraCore/job/release_1.3/job/ubuntu_check_eol_prtest/1835/console

All of that tasks that ran should have had release_1.4 in their URL, but the Style Check tasks were release_1.3.

• Verify that the style check tasks are correctly generated for release_1.4
• Track down why the wrong tasks were triggered

Not sure if this has caused any problems because these tasks are all the same and the diff (for files affected by the change) is taken by comparing against master (in the future this behavior will be changed to diff against the target branch (#962)), but I would be suspicious about whether whatever the problem is could cause problems in the future or affect more complex non-style checks.