Fix error due to missing method 'platform_family?'

[wndhydrnt]

This PR fixes a compatibility issue with Chef 12.6.0 and below.
A Chef run exits with the following error message:
No resource or method named `platform_family?' for `VaultCookbook::Provider::VaultService ""'

[wndhydrnt]

sous-chefs/consul#417 fixes the same issue in consul-cookbook. I based my changes on that PR.

[legal90]

LGTM with a small note: it fixes the compatibility with Chef 12.6.0 and below.

[codecov-io]

Codecov Report

Merging #96 into master will not change coverage.
The diff coverage is 0%.

@@         Coverage Diff          @@
##           master   #96   +/-   ##
====================================
  Coverage      53%   53%           
====================================
  Files           2     2           
  Lines         100   100           
====================================
  Hits           53    53           
  Misses         47    47

Impacted Files	Coverage Δ
libraries/vault_service.rb	52.27% <0%> (ø)	⬆️

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[wndhydrnt]

@legal90 Thanks for the hint. I've changed the wording in the commit message.

[wndhydrnt]

@legal90 I'd really like to get this merged so we can start using the cookbook. Anything else that needs to be done? Just let me know.

[legal90]

@wndhydrnt Thank you! I guess, the Travis CI build failure will be fixed by #97

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.