[r=rogpeppe] juju: use parallel.Try
[r=rogpeppe] juju: use parallel.Try

We use the new Try functionality to simplify the
logic somewhat when connecting to juju.

It will come more into its own when we connect
to multiple addresses.

https://codereview.appspot.com/37650048/
rogpeppe/juju,bac/juju,makyo/juju,frankban/juju,dooferlad/juju,cloud-green/juju,gabriel-samfira/juju,marcmolla/juju,gabriel-samfira/juju,cmars/juju,frankban/juju-tmp,bogdanteleaga/juju,tasdomas/juju,howbazaar/juju,davecheney/juju,tych0/juju,frobware/juju,dooferlad/juju,davecheney/juju,axw/juju,axw/juju,marcoceppi/juju,wwitzel3/juju,howbazaar/juju,mhilton/juju-juju,waigani/juju,marcoceppi/juju,kat-co/juju,fwereade/juju,cherylj/juju,makyo/juju,marcmolla/juju,jrwren/juju,mikemccracken/juju,anastasiamac/juju,mhilton/juju,frankban/juju-tmp,kat-co/juju,reedobrien/juju,kat-co/juju,bac/juju,davecheney/juju,cloud-green/juju,reedobrien/juju,marcoceppi/juju,Altoros/juju-vmware,bz2/juju,perrito666/juju,reedobrien/store,Altoros/juju-cloudsigma,sinzui/juju,ericsnowcurrently/juju,mhilton/juju,frankban/juju-tmp,Altoros/juju-cloudsigma,cmars/juju,gabriel-samfira/juju,sinzui/juju,waigani/juju,mikemccracken/juju,axw/juju,bogdanteleaga/juju,cmars/juju,AdamIsrael/juju,kat-co/juju,alesstimec/juju,mhilton/juju,waigani/juju,tych0/juju,cherylj/juju,mikemccracken/juju,waigani/juju,wwitzel3/juju,mhilton/juju-juju,mikemccracken/juju,alesstimec/juju,ericsnowcurrently/juju,alesstimec/juju,reedobrien/juju,reedobrien/juju,dimitern/juju,tsakas/juju,Altoros/juju-cloudsigma,makyo/juju,mhilton/juju-juju,cloud-green/juju,macgreagoir/juju,bz2/juju,bz2/juju,Altoros/juju-vmware,fwereade/juju,frankban/juju,anastasiamac/juju,gabriel-samfira/juju,mjs/juju,bz2/juju,ericsnowcurrently/juju,dimitern/juju,voidspace/juju,rogpeppe/juju,mjs/juju,bac/juju,anastasiamac/juju,frankban/juju-tmp,frobware/juju,Altoros/juju-cloudsigma,Altoros/juju-vmware,mattyw/juju,davecheney/juju,mjs/juju,bac/juju,tsakas/juju,bz2/juju,macgreagoir/juju,tsakas/juju,bogdanteleaga/juju,marcmolla/juju,jrwren/juju,tsakas/juju,marcmolla/juju,tych0/juju,perrito666/juju,mjs/juju,thomnico/juju,dooferlad/juju,mhilton/juju,marcmolla/juju,makyo/juju,perrito666/juju,mikemccracken/juju,anastasiamac/juju,marcoceppi/juju,wwitzel3/juju,howbazaar/juju,howbazaar/juju,jrwren/juju,tasdomas/juju,dooferlad/juju,mattyw/juju,anastasiamac/juju,howbazaar/juju,voidspace/juju,AdamIsrael/juju,thomnico/juju,alesstimec/juju,mattyw/juju,macgreagoir/juju,tych0/juju,fwereade/juju,mattyw/juju,macgreagoir/juju,macgreagoir/juju,cherylj/juju,dimitern/juju,tasdomas/juju,mjs/juju,fwereade/juju,bac/juju,voidspace/juju,voidspace/juju,rogpeppe/juju,sinzui/juju,frankban/juju,frobware/juju,frankban/juju,cmars/juju,sinzui/juju,dooferlad/juju,AdamIsrael/juju,cloud-green/juju,kat-co/juju,axw/juju,frankban/juju,axw/juju,bogdanteleaga/juju,dimitern/juju,Altoros/juju-vmware,thomnico/juju,perrito666/juju,gabriel-samfira/juju,ericsnowcurrently/juju,cherylj/juju,mjs/juju,wwitzel3/juju,AdamIsrael/juju,reedobrien/juju,tasdomas/juju,mhilton/juju-juju,perrito666/juju,dimitern/juju,thomnico/juju,alesstimec/juju,mjs/juju,ericsnowcurrently/juju