Enable lazy init for ext4 with devicemapper

Add file system options for config file, so that user can use
non-default file system parameters for the fs type of choice
Using file system options in config file overwrites the default
options already being used.

Signed-off-by: Alakesh Haloi <alakeshh@amazon.com>

snapshots/devmapper/config.go

@@ -50,6 +50,9 @@ type Config struct {
 
 	// Defines file system to use for snapshout device mount. Defaults to "ext4"
 	FileSystemType fsType `toml:"fs_type"`
+
+	// Defines optional file system options passed through config file
+	FsOptions string `toml:"fs_options"`
 }
 
 // LoadConfig reads devmapper configuration file from disk in TOML format