Format source code according to GNU indentation

No formal indentation style has been used in the source code. Apply the
GNU indentation style.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
Pass the last return value from pam to pam_end

The pam_status argument to pam_end should take the value returned by the
last PAM call. We store the return value from pam calls in the error
variable; it should be passed to pam_end.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>