correctly check for fixturedef when  merging
correctly check for fixturedef when  merging

--HG--
branch : fix-fixturedef-merge

vmalloc/dessert,doordash/pytest,hpk42/pytest,chillbear/pytest,malinoff/pytest,hunse/pytest,userzimmermann/pytest,takluyver/pytest,MichaelAquilina/pytest,jb098/pytest,pelme/pytest,ojake/pytest,ropez/pytest,userzimmermann/pytest,nicoddemus/pytest,pytest-dev/pytest,Carreau/pytest,MengJueM/pytest,flub/pytest,ionelmc/pytest,bukzor/pytest,ericdill/pytest,mdboom/pytest,bubenkoff/pytest,oleg-alexandrov/pytest,tomviner/pytest,ddboline/pytest,Carreau/pytest,inirudebwoy/pytest,tgoodlet/pytest,markshao/pytest,alfredodeza/pytest,chillbear/pytest,skylarjhdownes/pytest,nicoddemus/pytest,Haibo-Wang-ORG/pytest,ghostsquad/pytest,jaraco/pytest,vodik/pytest,icemac/pytest,etataurov/pytest,gabrielcnr/pytest,pfctdayelise/pytest,JonathonSonesen/pytest,omarkohl/pytest,omarkohl/pytest,Haibo-Wang-ORG/pytest,rouge8/pytest,MengJueM/pytest,nicoddemus/repo-test,Akasurde/pytest,chiller/pytest,vodik/pytest,pelme/pytest,inirudebwoy/pytest,txomon/pytest,Bachmann1234/pytest,mbirtwell/pytest,jb098/pytest,Bjwebb/pytest,mbirtwell/pytest,davidszotten/pytest,abusalimov/pytest,lukas-bednar/pytest,JonathonSonesen/pytest,mhils/pytest,oleg-alexandrov/pytest,bukzor/pytest,hackebrot/pytest,ionelmc/pytest,nicoddemus/repo-test,tomviner/pytest,hunse/pytest,codewarrior0/pytest,rmfitzpatrick/pytest,gabrielcnr/pytest,takluyver/pytest,codewarrior0/pytest,untitaker/pytest,ojake/pytest,rouge8/pytest,The-Compiler/pytest,wfxiang08/pytest,untitaker/pytest,Bjwebb/pytest,bubenkoff/pytest,lukas-bednar/pytest,Bachmann1234/pytest,ericdill/pytest,The-Compiler/pytest,mdboom/pytest,wfxiang08/pytest,tareqalayan/pytest,eli-b/pytest,doordash/pytest,ropez/pytest,hpk42/pytest,abusalimov/pytest,chiller/pytest,mhils/pytest,ghostsquad/pytest,RonnyPfannschmidt/pytest,icemac/pytest