worker/uniter: fix TestUniterUpgradeConflicts
worker/uniter: fix TestUniterUpgradeConflicts

Another attempt at fixing TestUniterUpgradeConflicts.
SetAgentStatus is called from the test in order to
avoid a race condition, however the call fails due to
an invalid/deprecated agent stauts being set. The
failure was silent, since the error wasn't checked.

Set to "idle" instead of "active".

dooferlad/juju,tsakas/juju,dimitern/juju,dooferlad/juju,bogdanteleaga/juju,bac/juju,anastasiamac/juju,howbazaar/juju,alesstimec/juju,axw/juju,marcmolla/juju,wwitzel3/juju,wwitzel3/juju,reedobrien/juju,macgreagoir/juju,dooferlad/juju,axw/juju,bogdanteleaga/juju,howbazaar/juju,dooferlad/juju,frankban/juju,perrito666/juju,cloud-green/juju,mjs/juju,mikemccracken/juju,kat-co/juju,ericsnowcurrently/juju,AdamIsrael/juju,gabriel-samfira/juju,kat-co/juju,dimitern/juju,mikemccracken/juju,makyo/juju,voidspace/juju,cloud-green/juju,marcmolla/juju,kat-co/juju,gabriel-samfira/juju,makyo/juju,macgreagoir/juju,mjs/juju,macgreagoir/juju,dimitern/juju,cloud-green/juju,fwereade/juju,bz2/juju,fwereade/juju,reedobrien/juju,anastasiamac/juju,axw/juju,tsakas/juju,alesstimec/juju,fwereade/juju,macgreagoir/juju,perrito666/juju,voidspace/juju,anastasiamac/juju,frankban/juju,kat-co/juju,reedobrien/juju,davecheney/juju,alesstimec/juju,perrito666/juju,perrito666/juju,bogdanteleaga/juju,fwereade/juju,alesstimec/juju,perrito666/juju,kat-co/juju,cloud-green/juju,mjs/juju,alesstimec/juju,bz2/juju,mikemccracken/juju,bac/juju,ericsnowcurrently/juju,waigani/juju,howbazaar/juju,marcmolla/juju,ericsnowcurrently/juju,dimitern/juju,frankban/juju,frankban/juju,axw/juju,reedobrien/juju,ericsnowcurrently/juju,axw/juju,anastasiamac/juju,makyo/juju,dimitern/juju,bz2/juju,tsakas/juju,wwitzel3/juju,wwitzel3/juju,bac/juju,ericsnowcurrently/juju,davecheney/juju,davecheney/juju,voidspace/juju,davecheney/juju,gabriel-samfira/juju,bz2/juju,frankban/juju,waigani/juju,mjs/juju,gabriel-samfira/juju,waigani/juju,mikemccracken/juju,mjs/juju,howbazaar/juju,tsakas/juju,macgreagoir/juju,mjs/juju,waigani/juju,bac/juju,howbazaar/juju,bz2/juju,gabriel-samfira/juju,AdamIsrael/juju,AdamIsrael/juju,bogdanteleaga/juju,anastasiamac/juju,dooferlad/juju,mikemccracken/juju,marcmolla/juju,reedobrien/juju,voidspace/juju,AdamIsrael/juju,marcmolla/juju,makyo/juju,bac/juju,mjs/juju