Fixed logging not occuring with Ubuntu 14.04

[philippfranke]

This patch is a fix for issue #365, where the logging is not writing
to /var/log/rexray/rexray.log.

Since os.Stderr is attached to TTY(!log.IsTerminal()) rexray doesn't
write to the log file so I removed cmd.Stderr.

[coveralls]

Changes Unknown when pulling 7476ad5 on philippfranke:fix_logging into * on emccode:master*.

[codecov-io]

Current coverage is 91.08%

Merging #373 into master will not affect coverage as of 2c244f4

@@            master    #373   diff @@
======================================
  Files            8       8       
  Stmts          729     729       
  Branches        14      14       
  Methods          0       0       
======================================
  Hit            664     664       
  Partial         14      14       
  Missed          51      51       

Review entire Coverage Diff as of 2c244f4

---

Uncovered Suggestions

1. +1.37% via ...re/drivers_volume.go#183...192
2. +1.23% via ...re/drivers_volume.go#344...352
3. +0.96% via ...re/drivers_volume.go#220...226
4. See 7 more...

Powered by Codecov. Updated on successful CI builds.

[akutz]

Hi @philippfranke,

I'm not sure we want to do this. I based this detection on the same detection in logrus, which recently updated its logic. Additionally, this apparently only happens on Ubuntu 14.04, so unless this patch has been tested this on all other, supported distros, this patch won't be accepted that will have possible side-effects for other distributions.

[clintkitson]

Definitely need to look into this one further. Thanks for the feedback so far and work towards a fix @philippfranke.

[clintkitson]

@akutz I tested this and I believe the fix does in fact take care of the issue and doesn't seem to represent any detrimental issues. Your call.

[akutz]

Hi @philippfranke / @clintonskitson,

I can cherry-pick @philippfranke's fix or he can close and reopen this PR against the release/0.3.3 branch. I could manually pull the patch over, but a merge would overwrite other bits on the release/0.3.3 branch as well. @philippfranke, it's your call here -- either reopen this PR against 0.3.3 or I can cherry-pick your commit across, and we'll just reflect in this PR what occurred.