kernel-install used to work without /proc mounted before the rewrite
in C. Let's restore that property by making sure we don't reopen
file descriptors via /proc. In this case, parse_env_file_fdv() calls
fdopen_independent() to get a FILE * for the given file descriptor
(which itself calls fd_reopen()). Let's avoid the call to
fdopen_independent() by using chase_and_fopenat_unlocked() which
gives us a FILE * immediately without having to reopen any file
descriptors.
Daan De Meyer
a061312324