Create readonly locks if the lockfile does not exists

Users are setting up readonly shares and sometimes they forget, or do
not even know that they need to create the lockfile.

Even in the quay.io/podman/stable images Dockerfile, I have to manually
create these files.

Fixes: #1029

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

pkg/lockfile/lockfile_unix.go

@@ -36,7 +36,7 @@ type lockfile struct {
 // necessary.
 func openLock(path string, ro bool) (fd int, err error) {
 	if ro {
-		fd, err = unix.Open(path, os.O_RDONLY|unix.O_CLOEXEC, 0)
+		fd, err = unix.Open(path, os.O_RDONLY|unix.O_CLOEXEC|os.O_CREATE, 0)
 	} else {
 		fd, err = unix.Open(path,
 			os.O_RDWR|unix.O_CLOEXEC|os.O_CREATE,