Fail properly when profile can't be accessed

Fail properly when profile can't be accessed

Make profile_init() return EACCESS or EPERM if one of those errors was
encountered when failing to open any of the specified profile files.
This causes krb5_init_os_context() to fail properly when krb5.conf is
unreadable, instead of treating that situation like a nonexistent
krb5.conf.

The library will continue to soldier on if one profile file is
readable and another is not.  This is deliberate as of r14116, whether
or not it's a good idea.

ticket: 6760

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24250 dc483132-0cff-0310-8789-dd5450dbe970