TestHelper: Run tests in their own process group
TestHelper: Run tests in their own process group

Fixes https://github.com/coala-analyzer/coala/issues/697

FeodorFitsner/coala,CruiseDevice/coala,vinc456/coala,netman92/coala,rresol/coala,SanketDG/coala,AdeshAtole/coala,meetmangukiya/coala,NalinG/coala,damngamerz/coala,yashtrivedi96/coala,meetmangukiya/coala,yashtrivedi96/coala,coala/coala,abhiroyg/coala,ManjiriBirajdar/coala,Nosferatul/coala,AbdealiJK/coala,scottbelden/coala,yashLadha/coala,shreyans800755/coala,kartikeys98/coala,netman92/coala,jayvdb/coala,swatilodha/coala,coala/coala,andreimacavei/coala,Asalle/coala,NalinG/coala,scottbelden/coala,JohnS-01/coala,netman92/coala,SambitAcharya/coala,Shade5/coala,Tanmay28/coala,shreyans800755/coala,refeed/coala,CruiseDevice/coala,SanketDG/coala,stevemontana1980/coala,coala/coala,Uran198/coala,djkonro/coala,stevemontana1980/coala,arush0311/coala,scriptnull/coala,d6e/coala,Balaji2198/coala,arafsheikh/coala,FeodorFitsner/coala,Tanmay28/coala,Asnelchristian/coala,scriptnull/coala,swatilodha/coala,rimacone/testing2,aptrishu/coala,yland/coala,NalinG/coala,yland/coala,JohnS-01/coala,rresol/coala,mr-karan/coala,SambitAcharya/coala,rimacone/testing2,AbdealiJK/coala,NalinG/coala,arush0311/coala,Balaji2198/coala,RJ722/coala,SambitAcharya/coala,karansingh1559/coala,sudheesh001/coala,sophiavanvalkenburg/coala,sudheesh001/coala,scriptnull/coala,arafsheikh/coala,tushar-rishav/coala,FeodorFitsner/coala,MariosPanag/coala,Tanmay28/coala,vinc456/coala,swatilodha/coala,NalinG/coala,MattAllmendinger/coala,nemaniarjun/coala,RJ722/coala,Shade5/coala,MattAllmendinger/coala,NalinG/coala,SambitAcharya/coala,SambitAcharya/coala,tltuan/coala,Tanmay28/coala,lonewolf07/coala,scriptnull/coala,NiklasMM/coala,tushar-rishav/coala,abhiroyg/coala,karansingh1559/coala,arjunsinghy96/coala,NiklasMM/coala,rimacone/testing2,sophiavanvalkenburg/coala,ManjiriBirajdar/coala,JohnS-01/coala,ayushin78/coala,saurabhiiit/coala,shreyans800755/coala,incorrectusername/coala,mr-karan/coala,MariosPanag/coala,coala-analyzer/coala,damngamerz/coala,svsn2117/coala,MariosPanag/coala,stevemontana1980/coala,abhiroyg/coala,Shade5/coala,mr-karan/coala,andreimacavei/coala,sagark123/coala,sagark123/coala,tltuan/coala,coala-analyzer/coala,tltuan/coala,svsn2117/coala,nemaniarjun/coala,lonewolf07/coala,arjunsinghy96/coala,sils1297/coala,MattAllmendinger/coala,saurabhiiit/coala,lonewolf07/coala,karansingh1559/coala,Asalle/coala,Balaji2198/coala,SanketDG/coala,Nosferatul/coala,Uran198/coala,yashtrivedi96/coala,yashLadha/coala,aptrishu/coala,nemaniarjun/coala,impmihai/coala,incorrectusername/coala,arjunsinghy96/coala,CruiseDevice/coala,sudheesh001/coala,Asnelchristian/coala,andreimacavei/coala,tushar-rishav/coala,jayvdb/coala,impmihai/coala,ManjiriBirajdar/coala,dagdaggo/coala,arush0311/coala,refeed/coala,AbdealiJK/coala,refeed/coala,djkonro/coala,vinc456/coala,rresol/coala,damngamerz/coala,sagark123/coala,AdeshAtole/coala,scottbelden/coala,dagdaggo/coala,impmihai/coala,kartikeys98/coala,svsn2117/coala,NalinG/coala,arafsheikh/coala,incorrectusername/coala,aptrishu/coala,jayvdb/coala,saurabhiiit/coala,sophiavanvalkenburg/coala,scriptnull/coala,ayushin78/coala,Asnelchristian/coala,Tanmay28/coala,SambitAcharya/coala,sils1297/coala,sils1297/coala,NiklasMM/coala,SambitAcharya/coala,meetmangukiya/coala,coala-analyzer/coala,djkonro/coala,Tanmay28/coala,RJ722/coala,d6e/coala,AdeshAtole/coala,Nosferatul/coala,dagdaggo/coala,d6e/coala,kartikeys98/coala,Uran198/coala,scriptnull/coala,Tanmay28/coala,scriptnull/coala,yashLadha/coala,yland/coala,Tanmay28/coala,ayushin78/coala,Asalle/coala