Fix test_artists test with respect to hashing and set behaveviour
Fix test_artists test with respect to hashing and set behaveviour

mokieyue/mopidy,mokieyue/mopidy,mokieyue/mopidy,jmarsik/mopidy,woutervanwijk/mopidy,hkariti/mopidy,ZenithDK/mopidy,bencevans/mopidy,bacontext/mopidy,jmarsik/mopidy,quartz55/mopidy,jcass77/mopidy,ZenithDK/mopidy,priestd09/mopidy,vrs01/mopidy,SuperStarPL/mopidy,kingosticks/mopidy,pacificIT/mopidy,hkariti/mopidy,pacificIT/mopidy,kingosticks/mopidy,bacontext/mopidy,ali/mopidy,tkem/mopidy,glogiotatidis/mopidy,glogiotatidis/mopidy,dbrgn/mopidy,ali/mopidy,vrs01/mopidy,adamcik/mopidy,glogiotatidis/mopidy,glogiotatidis/mopidy,SuperStarPL/mopidy,jcass77/mopidy,priestd09/mopidy,jodal/mopidy,quartz55/mopidy,woutervanwijk/mopidy,swak/mopidy,SuperStarPL/mopidy,jcass77/mopidy,liamw9534/mopidy,quartz55/mopidy,hkariti/mopidy,adamcik/mopidy,SuperStarPL/mopidy,jmarsik/mopidy,diandiankan/mopidy,diandiankan/mopidy,bencevans/mopidy,ali/mopidy,ali/mopidy,rawdlite/mopidy,ZenithDK/mopidy,swak/mopidy,mopidy/mopidy,diandiankan/mopidy,priestd09/mopidy,mopidy/mopidy,tkem/mopidy,abarisain/mopidy,jodal/mopidy,swak/mopidy,dbrgn/mopidy,rawdlite/mopidy,liamw9534/mopidy,tkem/mopidy,mokieyue/mopidy,jodal/mopidy,adamcik/mopidy,quartz55/mopidy,rawdlite/mopidy,vrs01/mopidy,bencevans/mopidy,tkem/mopidy,pacificIT/mopidy,swak/mopidy,jmarsik/mopidy,pacificIT/mopidy,hkariti/mopidy,ZenithDK/mopidy,bacontext/mopidy,dbrgn/mopidy,kingosticks/mopidy,vrs01/mopidy,dbrgn/mopidy,rawdlite/mopidy,bencevans/mopidy,bacontext/mopidy,mopidy/mopidy,diandiankan/mopidy,abarisain/mopidy