worker/migrationmaster: Tweaked a log level
worker/migrationmaster: Tweaked a log level

Not being able to remove a model from the target controller isn't fatal
and is expected in some cases.

frankban/juju,ericsnowcurrently/juju,kat-co/juju,macgreagoir/juju,gabriel-samfira/juju,AdamIsrael/juju,dimitern/juju,dimitern/juju,dimitern/juju,mjs/juju,reedobrien/juju,mjs/juju,gabriel-samfira/juju,perrito666/juju,AdamIsrael/juju,axw/juju,howbazaar/juju,reedobrien/juju,dimitern/juju,mjs/juju,AdamIsrael/juju,marcmolla/juju,howbazaar/juju,bac/juju,marcmolla/juju,bz2/juju,marcmolla/juju,waigani/juju,kat-co/juju,axw/juju,gabriel-samfira/juju,bac/juju,howbazaar/juju,waigani/juju,gabriel-samfira/juju,anastasiamac/juju,kat-co/juju,anastasiamac/juju,frankban/juju,kat-co/juju,mjs/juju,axw/juju,howbazaar/juju,perrito666/juju,reedobrien/juju,waigani/juju,frankban/juju,howbazaar/juju,axw/juju,bac/juju,mikemccracken/juju,alesstimec/juju,mjs/juju,mikemccracken/juju,macgreagoir/juju,perrito666/juju,marcmolla/juju,axw/juju,ericsnowcurrently/juju,mjs/juju,bz2/juju,bz2/juju,mjs/juju,kat-co/juju,alesstimec/juju,alesstimec/juju,reedobrien/juju,gabriel-samfira/juju,anastasiamac/juju,bz2/juju,alesstimec/juju,mikemccracken/juju,waigani/juju,perrito666/juju,marcmolla/juju,perrito666/juju,frankban/juju,macgreagoir/juju,bz2/juju,AdamIsrael/juju,reedobrien/juju,dimitern/juju,frankban/juju,bac/juju,ericsnowcurrently/juju,anastasiamac/juju,ericsnowcurrently/juju,ericsnowcurrently/juju,macgreagoir/juju,mikemccracken/juju,anastasiamac/juju,bac/juju,macgreagoir/juju,mikemccracken/juju,alesstimec/juju