add test for --maxfail=NUM overiding -x
add test for --maxfail=NUM overiding -x

tomviner/pytest,txomon/pytest,flub/pytest,RonnyPfannschmidt/pytest,tgoodlet/pytest,etataurov/pytest,malinoff/pytest,tomviner/pytest,hpk42/pytest,The-Compiler/pytest,nicoddemus/pytest,alfredodeza/pytest,hpk42/pytest,tareqalayan/pytest,pytest-dev/pytest,rmfitzpatrick/pytest,jaraco/pytest,ddboline/pytest,markshao/pytest,MichaelAquilina/pytest,eli-b/pytest,skylarjhdownes/pytest,vmalloc/dessert,davidszotten/pytest,hackebrot/pytest,The-Compiler/pytest,pfctdayelise/pytest,Akasurde/pytest,nicoddemus/pytest