ConfigurationGathering: Remove mutable argument
ConfigurationGathering: Remove mutable argument

ConfigurationGathering has a mutable argument which is causing
trouble with pytest being able to modify the arguments there.
This sets that value to None and replaces it inside the function.

Fixes https://github.com/coala-analyzer/coala/issues/1352

kartikeys98/coala,sils1297/coala,shreyans800755/coala,MattAllmendinger/coala,arafsheikh/coala,CruiseDevice/coala,yland/coala,saurabhiiit/coala,scriptnull/coala,Asnelchristian/coala,scottbelden/coala,ManjiriBirajdar/coala,yashtrivedi96/coala,JohnS-01/coala,SambitAcharya/coala,Shade5/coala,shreyans800755/coala,nemaniarjun/coala,meetmangukiya/coala,sudheesh001/coala,lonewolf07/coala,mr-karan/coala,rresol/coala,djkonro/coala,tushar-rishav/coala,scriptnull/coala,AdeshAtole/coala,arjunsinghy96/coala,NalinG/coala,djkonro/coala,rresol/coala,Balaji2198/coala,scriptnull/coala,Balaji2198/coala,stevemontana1980/coala,dagdaggo/coala,SambitAcharya/coala,kartikeys98/coala,tushar-rishav/coala,nemaniarjun/coala,CruiseDevice/coala,d6e/coala,coala-analyzer/coala,saurabhiiit/coala,d6e/coala,tushar-rishav/coala,Asalle/coala,scriptnull/coala,MariosPanag/coala,coala/coala,lonewolf07/coala,svsn2117/coala,yashLadha/coala,dagdaggo/coala,tltuan/coala,impmihai/coala,swatilodha/coala,stevemontana1980/coala,abhiroyg/coala,swatilodha/coala,SanketDG/coala,sils1297/coala,arush0311/coala,rimacone/testing2,ManjiriBirajdar/coala,Asnelchristian/coala,Balaji2198/coala,yashtrivedi96/coala,abhiroyg/coala,SambitAcharya/coala,MariosPanag/coala,karansingh1559/coala,ayushin78/coala,coala-analyzer/coala,AbdealiJK/coala,Nosferatul/coala,scriptnull/coala,NalinG/coala,coala-analyzer/coala,karansingh1559/coala,sudheesh001/coala,NalinG/coala,AbdealiJK/coala,NalinG/coala,mr-karan/coala,abhiroyg/coala,Asalle/coala,impmihai/coala,incorrectusername/coala,Nosferatul/coala,sophiavanvalkenburg/coala,RJ722/coala,SanketDG/coala,sagark123/coala,NalinG/coala,sagark123/coala,AdeshAtole/coala,MattAllmendinger/coala,SambitAcharya/coala,kartikeys98/coala,refeed/coala,lonewolf07/coala,yland/coala,tltuan/coala,arjunsinghy96/coala,SambitAcharya/coala,NiklasMM/coala,vinc456/coala,mr-karan/coala,arafsheikh/coala,aptrishu/coala,sophiavanvalkenburg/coala,netman92/coala,NalinG/coala,meetmangukiya/coala,Nosferatul/coala,coala/coala,scriptnull/coala,stevemontana1980/coala,JohnS-01/coala,netman92/coala,Shade5/coala,meetmangukiya/coala,NalinG/coala,coala/coala,d6e/coala,sils1297/coala,incorrectusername/coala,AdeshAtole/coala,MariosPanag/coala,sophiavanvalkenburg/coala,yashLadha/coala,jayvdb/coala,SanketDG/coala,scottbelden/coala,NiklasMM/coala,SambitAcharya/coala,shreyans800755/coala,rimacone/testing2,swatilodha/coala,refeed/coala,arush0311/coala,tltuan/coala,damngamerz/coala,nemaniarjun/coala,damngamerz/coala,Uran198/coala,yashtrivedi96/coala,RJ722/coala,rresol/coala,RJ722/coala,saurabhiiit/coala,CruiseDevice/coala,MattAllmendinger/coala,Uran198/coala,NiklasMM/coala,ayushin78/coala,SambitAcharya/coala,karansingh1559/coala,rimacone/testing2,JohnS-01/coala,netman92/coala,Asnelchristian/coala,arjunsinghy96/coala,dagdaggo/coala,vinc456/coala,Asalle/coala,impmihai/coala,refeed/coala,incorrectusername/coala,sagark123/coala,ayushin78/coala,Shade5/coala,damngamerz/coala,Uran198/coala,scriptnull/coala,jayvdb/coala,jayvdb/coala,sudheesh001/coala,ManjiriBirajdar/coala,scottbelden/coala,aptrishu/coala,vinc456/coala,arush0311/coala,djkonro/coala,yland/coala,arafsheikh/coala,svsn2117/coala,yashLadha/coala,svsn2117/coala,AbdealiJK/coala,aptrishu/coala