dfg: fix wrong return value of _need_to_ignore
dfg: fix wrong return value of _need_to_ignore

iamahuman/angr,tyb0807/angr,tyb0807/angr,chubbymaggie/angr,angr/angr,angr/angr,f-prettyland/angr,chubbymaggie/angr,haylesr/angr,axt/angr,f-prettyland/angr,iamahuman/angr,iamahuman/angr,schieb/angr,schieb/angr,schieb/angr,axt/angr,f-prettyland/angr,axt/angr,angr/angr,tyb0807/angr,haylesr/angr,chubbymaggie/angr