Limit rlim_max in rlimit_nofile_safe() to nr_open

We might inherit a max rlim value that's larger than the kernel's
maximum (nr_open). This will cause setrlimit() to fail as the given
maximum is larger than the kernel's maximum. To get around this,
let's limit the max rlim we pass to rlimit() to the value of nr_open.

Should fix #28965

(cherry picked from commit f470dafddcd688c3ea6031d4bbcbf934fd094711)