lp:~xiaoxin-yang/cloud-init

Author: Chad Smith
Author Date: 2017-11-30 20:09:30 UTC

ec2: Fix sandboxed dhclient background process cleanup.

There is a race condition where our sandboxed dhclient properly writes a
lease file but has not yet written a pid file. If the sandbox temporary
directory is torn down before the dhclient subprocess writes a pidfile
DataSourceEc2Local gets a traceback and the instance will fallback to
DataSourceEc2 in the init-network stage. This wastes boot cycles we'd
rather not spend.

Fix handling of sandboxed dhclient to wait for both pidfile and leasefile
before proceding. If either file doesn't show in 5 seconds, log a warning
and return empty lease results {}.

LP: #1735331