rgw_file: fix non-posix errcode EINVAL to ENAMETOOLONG

rgw_file: fix non-posix errcode EINVAL to ENAMETOOLONG

When exec the following cmd in RGW FS, we get EINVAL:
> mkdir <very/long/path> -p
Because the path name exceeds 1024 which is the max object name
length for s3.
Actually we should get ENAMETOOLONG here in posix, so we could
wrap the name check functions and check the exact errcode
for posix.

Signed-off-by: Gui Hecheng <guihecheng@cmss.chinamobile.com>