conf: use explicit signage in bit field

src/lxc/conf.h

@@ -197,12 +197,12 @@ typedef enum lxc_mount_options_t {
 __hidden extern const char *lxc_mount_options_info[LXC_MOUNT_MAX];
 
 struct lxc_mount_options {
-	int create_dir : 1;
-	int create_file : 1;
-	int optional : 1;
-	int relative : 1;
-	int recursive : 1;
-	int bind : 1;
+	unsigned int create_dir : 1;
+	unsigned int create_file : 1;
+	unsigned int optional : 1;
+	unsigned int relative : 1;
+	unsigned int recursive : 1;
+	unsigned int bind : 1;
 	char userns_path[PATH_MAX];
 	unsigned long mnt_flags;
 	unsigned long prop_flags;