Keep image content if persistentVolume.enabled is false

[pchico83]

Related to #764

If persistentVolume is not enabled, this PR does not mount an emptyDir on the working dir, and the content of the image is not lost. In a later iteration this will be the default behavior

[derek]

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[codecov]

Codecov Report

Merging #782 into master will increase coverage by 0.03%.
The diff coverage is 53.33%.

@@            Coverage Diff             @@
##           master     #782      +/-   ##
==========================================
+ Coverage   32.36%   32.39%   +0.03%     
==========================================
  Files          63       63              
  Lines        4944     4951       +7     
==========================================
+ Hits         1600     1604       +4     
- Misses       3212     3215       +3     
  Partials      132      132

Impacted Files	Coverage Δ
cmd/up.go	0% <0%> (ø)	⬆️
pkg/model/dev.go	65.17% <80%> (+0.02%)	⬆️

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