V2 Fix libpam's chmod

V2 Fix libpam's chmod

The libpam's has an error when generating the rootfs:

chmod: cannot access `/usr/sbin/unix_chkpwd': No such file or directory

This is because the following code in libpam_1.1.5.bb:

pkg_postinst_pam-plugin-unix () {
    # below is necessary to allow unix_chkpwd get user info from shadow file
    # on lsb images
    chmod 4755 ${sbindir}/unix_chkpwd
}

This is to set the setuid permission for unix_chkpwd (the lsb test
requires this), but it lacks a "${D}", and we can do this in the install
stage.

[YOCTO #2049]

(From OE-Core rev: 0725c7f01b173b1cc2090f4a03a274c7017b8a1a)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>