Upgrade libmachine to master

This includes the fixes that was previously on
the github.com/machine-drivers/machine master:

6f34be4 Allow localized names for Virtual Switch
3a0d935 Fix broken IsVTXDisabled detection on AMD CPU

go.mod

@@ -14,7 +14,7 @@ require (
 	github.com/cpuguy83/go-md2man v1.0.4 // indirect
 	github.com/docker/docker v1.13.1 // indirect
 	github.com/docker/go-units v0.0.0-20170127094116-9e638d38cf69
-	github.com/docker/machine v0.16.1
+	github.com/docker/machine v0.16.1-0.20190718054102-a555e4f7a8f5
 	github.com/elazarl/goproxy v0.0.0-20190421051319-9d40249d3c2f
 	github.com/elazarl/goproxy/ext v0.0.0-20190421051319-9d40249d3c2f // indirect
 	github.com/fatih/color v1.7.0 // indirect

go.sum

@@ -26,8 +26,8 @@ github.com/docker/docker v1.13.1 h1:IkZjBSIc8hBjLpqeAbeE5mca5mNgeatLHBy3GO78BWo=
 github.com/docker/docker v1.13.1/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
 github.com/docker/go-units v0.0.0-20170127094116-9e638d38cf69 h1:N4WAsrRIb+4U1yIwJO3FMrLnrr61ael894nygpViQTU=
 github.com/docker/go-units v0.0.0-20170127094116-9e638d38cf69/go.mod h1:fgPhTUdO+D/Jk86RDLlptpiXQzgHJF7gydDDbaIK4Dk=
-github.com/docker/machine v0.16.1 h1:zrgroZounGVkxLmBqMyc1uT2GgapXVjIWHCfBf0udrA=
-github.com/docker/machine v0.16.1/go.mod h1:I8mPNDeK1uH+JTcUU7X0ZW8KiYz0jyAgNaeSJ1rCfDI=
+github.com/docker/machine v0.16.1-0.20190718054102-a555e4f7a8f5 h1:5OiV/JwT55JRKNJsM9HZrTlJH/TRp97Ee89ahtB78+w=
+github.com/docker/machine v0.16.1-0.20190718054102-a555e4f7a8f5/go.mod h1:I8mPNDeK1uH+JTcUU7X0ZW8KiYz0jyAgNaeSJ1rCfDI=
 github.com/elazarl/goproxy v0.0.0-20190421051319-9d40249d3c2f h1:8GDPb0tCY8LQ+OJ3dbHb5sA6YZWXFORQYZx5sdsTlMs=
 github.com/elazarl/goproxy v0.0.0-20190421051319-9d40249d3c2f/go.mod h1:/Zj4wYkgs4iZTTu3o/KG3Itv/qCCa8VVMlb3i9OVuzc=
 github.com/elazarl/goproxy/ext v0.0.0-20190421051319-9d40249d3c2f h1:AUj1VoZUfhPhOPHULCQQDnGhRelpFWHMLhQVWDsS0v4=