Added tests for unknown flags
Added tests for unknown flags

sysbot/go-flags,fuchsia-mirror/third_party-github.com-jessevdk-go-flags,fuchsia-mirror/third_party-github.com-jessevdk-go-flags,cmars/tools,cmars/tools,conseweb/go-flags,cmars/tools,FactomProject/go-flags,jessevdk/go-flags,sourcegraph/go-flags,zenoss/go-flags,jessevdk/go-flags,abates/go-flags,svent/go-flags,conseweb/go-flags,svent/go-flags,abates/go-flags,FactomProject/go-flags,sourcegraph/go-flags,zenoss/go-flags,sysbot/go-flags,cmars/tools