podman: set volatile storage flag for --rm containers

volatile containers are a storage optimization that disables *sync()
syscalls for the container rootfs.

If a container is created with --rm, then automatically set the
volatile storage flag as anyway the container won't persist after a
reboot or machine crash.

[NO TESTS NEEDED]

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/specgen/generate/container_create.go

@@ -194,6 +194,9 @@ func createContainerOptions(ctx context.Context, rt *libpod.Runtime, s *specgen.
 	if s.Umask != "" {
 		options = append(options, libpod.WithUmask(s.Umask))
 	}
+	if s.Volatile {
+		options = append(options, libpod.WithVolatile())
+	}
 
 	useSystemd := false
 	switch s.Systemd {

pkg/specgen/specgen.go

@@ -256,6 +256,9 @@ type ContainerStorageConfig struct {
 	// Secrets are the secrets that will be added to the container
 	// Optional.
 	Secrets []string `json:"secrets,omitempty"`
+	// Volatile specifies whether the container storage can be optimized
+	// at the cost of not syncing all the dirty files in memory.
+	Volatile bool `json:"volatile,omitempty"`
 }
 
 // ContainerSecurityConfig is a container's security features, including