[AutoQA] #283: Update all koji RPM downloading code to use get_nvr_rpms

[fedora-badges]

#283: Update all koji RPM downloading code to use get_nvr_rpms
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 Reporter:  tflink  |       Owner:  tflink     
     Type:  task    |      Status:  new        
 Priority:  minor   |   Milestone:  Finger Food
Component:  tests   |    Keywords:             
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 With the recent fix for #265, there is now a convenience method to
 download RPMs from koji.

Update test code to use this new method in order to reduce code
 duplication.

[fedora-badges]

#283: Update all koji RPM downloading code to use get_nvr_rpms
--------------------+-------------------------------------------------------
 Reporter:  tflink  |        Owner:  tflink     
     Type:  task    |       Status:  new        
 Priority:  minor   |    Milestone:  Finger Food
Component:  tests   |   Resolution:             
 Keywords:          |  
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Comment (by kparal):

Also, if downloading packages is mentioned in some
 documentation/templates/examples, it would be nice to update it there too.