lvm_support: update fact to use --no-headings

[b4ldr]

I noticed upgrading that the lvm_vg_#{vg}_pv facts dose not use the --no-headings switch like the other facts.

This PR adds the --no-headings switch and simplifies the collection

[codecov-io]

Codecov Report

Merging #259 (c248f64) into master (cada6d4) will not change coverage. The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master     #259   +/-   ##
=======================================
  Coverage   72.96%   72.96%           
=======================================
  Files          17       17           
  Lines         773      773           
=======================================
  Hits          564      564           
  Misses        209      209           

Impacted Files	Coverage Δ
lib/facter/lvm_support.rb	76.47% <0.00%> (ø)

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