getlogin_r: return early when linux sentinel value is set
When there is no login uid Linux sets /proc/self/loginid to the sentinel
value of, (uid_t) -1. If this is set we can return early and avoid
needlessly looking up the sentinel value in any configured nss
databases.
Checked on aarch64-linux-gnu.
* sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid): Return
early when linux sentinel value is set.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
(cherry picked from commit
cc8a1620eb97ccddd337d157263c13c57b39ab71)