Squashed 'external/workload-automation/' changes from 37f4d330..9edb6b20

9edb6b20 postgres_schemas: Add rules for cascading deletes
879a4916 README: Update with more specific supported python version.
7086fa6b target: Force consistent logcat format
716e59da framework/target: Add logcat buffer wrap detection
08fcc7d3 fw/getters: Fix typo
684121e2 fw: Replace usage of file locking with atomic writes
0c1229df utils/misc: Implement atomic writes
615cbbc9 fw/target_info: Prevent multiple parses of the target_info_cache
1425a6f6 Implement caching of ApkInfo
4557da2f utils/android: Implement a Podable wrapper of ApkInfo
7cf5fbd8 framework, tests: Correct signal disconnection
3f5a31de commands: Add report command
7c6ebfb4 framework: Have Job hold its own JobState
8640f4f6 framework: Add serializing Job status setter
46096536 framework: Fix serialized job retries set to 0
d4057367 tests: Add run state testbench
ef6cffd8 travis: Limit the maximum version of isort

git-subtree-dir: external/workload-automation
git-subtree-split: 9edb6b20f07cbc06897298b591fb3685c9507fc8