New EBS config parameter for using larger device ranges

[thevilledev]

This proposed change has been previously discussed on these issues:

• Device attachment issues: AWS EBS stuck attachments DOS libstorage server. #773
• Proposed change to modify device range from /dev/xvd[f-p] to /dev/xvd[b-c][a-z]: Support for more device nodes with EBS volumes thecodeteam/libstorage#598

I've now rebased the libstorage-specific change to the current REX-Ray master, since libstorage will be merged into this project. This change is targeted to the next REX-Ray version, which will be 0.10. Large device range has been introduced as a EBS configuration parameter useLargeDeviceRange which is false by default.

In order to workaround possible ghost device issues the device namespace is now iterated in a random order. This affects default behaviour as well.

In order to test this change both server and client-side re-configuration is required. Server configuration (in terms of EBS) should look like this:

ebs:
  accessKey:      foo
  secretKey:      bar
  region:         us-east-1
  maxRetries: 10
  statusTimeout: 240s
  statusInitialDelay: 50ms
  statusMaxAttempts: 10
  useLargeDeviceRange: true

Client configuration:

ebs:
  useLargeDeviceRange: true

Pre-built binary for amd64 architecture is available here: https://github.com/vtorhonen/rexray/releases/tag/v0.10.0-lds

Let me know if there's anything to fix/add.

[CLAassistant]

All committers have signed the CLA.

[codecov-io]

Codecov Report

Merging #996 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #996   +/-   ##
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  Coverage   34.11%   34.11%           
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  Files          36       36           
  Lines        2896     2896           
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  Hits          988      988           
  Misses       1806     1806           
  Partials      102      102

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[akutz]

This looks amazing. Great work @vtorhonen!