Improve tests for utils.retry_over_time
Improve tests for utils.retry_over_time

Split up the existing two tests run under one method into two methods so
we will be able to later test other permutations of the various options,
namely the retry-related stuff.

numb3r3/kombu,xujun10110/kombu,andresriancho/kombu,mverrilli/kombu,iris-edu-int/kombu,bmbouter/kombu,romank0/kombu,ZoranPavlovic/kombu,romank0/kombu,celery/kombu,daevaorn/kombu,numb3r3/kombu,depop/kombu,cce/kombu,Elastica/kombu,mathom/kombu,depop/kombu,tkanemoto/kombu,tkanemoto/kombu,iris-edu-int/kombu,jindongh/kombu,bmbouter/kombu,ZoranPavlovic/kombu,mverrilli/kombu,daevaorn/kombu,urbn/kombu,xujun10110/kombu,alex/kombu,alex/kombu,mathom/kombu,cce/kombu,Elastica/kombu,jindongh/kombu,andresriancho/kombu