commands/probe: Fix resource leaks

commands/probe: Fix resource leaks

Commit 1fc860bb76bb (commands/probe: Fix a resource leak when probing disks),
missed other cases where grub_device_close() should be called before a return
statement is called. Also found that grub_disk_close() wasn't being called when
an error is being returned. To avoid conflict with grub_errno, grub_error_push()
should be called before either grub_device_close() or grub_disk_close() is
called and grub_error_pop() should be called before grub_errno is returned.

Fixes: 1fc860bb76bb (commands/probe: Fix a resource leak when probing disks)
Fixes: CID 292443
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>