Work around glibc bug 11941 (dlclose assertion)

When building against glibc 2.24 or earlier, suppress calls to
dlclose() to prevent the assertion failure "_dl_close: Assertion
`map->l_init_called' failed" at process exit.  We need this workaround
to enable automated tests that load GSSAPI modules.

https://github.com/krb5/krb5/commit/bf5953c549a6d279977df69ffe89b2ba51460eaf
Author: Greg Hudson <ghudson@mit.edu>
Commit: bf5953c549a6d279977df69ffe89b2ba51460eaf
Branch: master
 src/util/support/plugins.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)