Log memory failures - print a warning about possible OOMs
Log memory failures - print a warning about possible OOMs

Summary:
`memory.failcnt` is an indicator of pushing past memory limits. This is not guaranteed to manifest
as an OOM kill or cause errors. It is possible for memory pressure to be relieved by flushing to
disk, avoiding OOM kills.

Reviewers: kylec

Reviewed By: kylec

Subscribers: changesbot

Differential Revision: https://tails.corp.dropbox.com/D178191

dropbox/changes-client,dropbox/changes-client