Apply pylint to check_boot_jars.py

1. Run pyformat scripts/check_boot_jars/check_boot_jars.py -s 4
--force_quote_type none -i to fix formatting.
3. use pylint: disable=<X> where fixes are not obvious

Test: m check_boot_jars
Test: pylint --rcfile tools/repohooks/tools/pylintrc
scripts/check_boot_jars/check_boot_jars.py
Bug: 195738175

Change-Id: I0f86d95e0d174c9f87a2872dedaa65cd3e814246