Revert "fix(coreos): tune etcd to address high disk i/o environments"

In testing, this commit causes more harm than good, and
results in etcd/fleet going haywire.

This reverts commit 4f95cb82c87e75c6492ce0084961d57b0d70ae31.
Merge pull request #2663 from carmstrong/revert-etcd_timeout

Revert "fix(coreos): tune etcd to address high disk i/o environments"
Revert "ref(controller): use /bin/sh for better portability"

This reverts commit a897ddb2aba0dbc2068599a9263a21077f13679c.
Revert "ref(tests): switch to example-dockerfile-http app"

This reverts commit d4b9ca897f5535733cd89daac08ec61baf0d1f20.