btrfs-progs: close all fs_devices before exit in some commands

btrfs-progs: close all fs_devices before exit in some commands

mkfs creates more than one fs_devices in fs_uuids.
1: one is for file system being created
2: others are created in test_dev_for_mkfs in order to check mount point
   test_dev_for_mkfs()-> ... -> btrfs_scan_one_device()

Current code only closes 1, and this patch also closes in case 2.

Similar problem exist in other tools, eg.::

 cmd-check.c: the function is:
 cmd_check()->check_mounted()-> ... -> btrfs_scan_one_device()
 ...

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>