Move more functionality to helper methods and properties
Move more functionality to helper methods and properties

More passphrase_cmd and software_license_agreement over to helper methods that we can potentially test later on.
Improve the requires EULA error message
Use a default value for volumes_dir that sets it to the value of the app property instead of creating a variable later.

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

jaymzh/chef,gene1wood/chef,nvwls/chef,Tensibai/chef,chef/chef,MsysTechnologiesllc/chef,martinisoft/chef,jaymzh/chef,nvwls/chef,nvwls/chef,mattray/chef,higanworks/chef,chef/chef,tas50/chef-1,martinisoft/chef,tomdoherty/chef,higanworks/chef,mattray/chef,MsysTechnologiesllc/chef,gene1wood/chef,higanworks/chef,tomdoherty/chef,nvwls/chef,jaymzh/chef,Tensibai/chef,higanworks/chef,mwrock/chef,chef/chef,Tensibai/chef,gene1wood/chef,martinisoft/chef,nvwls/chef,Tensibai/chef,mattray/chef,mattray/chef,higanworks/chef,tomdoherty/chef,MsysTechnologiesllc/chef,tas50/chef-1,gene1wood/chef,mattray/chef,MsysTechnologiesllc/chef,jaymzh/chef,mwrock/chef,mwrock/chef,chef/chef,tas50/chef-1,martinisoft/chef,tas50/chef-1,Tensibai/chef,tomdoherty/chef,tomdoherty/chef,nvwls/chef,martinisoft/chef,mwrock/chef