ceph: Use strscpy() instead of strcpy() in __get_snap_name()

ceph: Use strscpy() instead of strcpy() in __get_snap_name()

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors [1].

This fixes checkpatch warning:
    WARNING: Prefer strscpy over strcpy

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy

[ idryomov: formatting ]

Signed-off-by: Abdul Rahim <abdul.rahim@myyahoo.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>