Fix #3036: Add /usr/etc/pyenv.d to hook path

The directory /usr/etc is an optional directory and used by
Fedora, RHEL 9, and openSUSE. The purpose of /usr/etc is to store
distribution-provided configuration files that can be overridden
by user-modified files in /etc.

/usr/etc is not in FHS. However, as Torsten stated in his comment
(https://github.com/thkukuk/atomic-updates_and_etc/issues/2#issuecomment-524848666)
"[FHS] is currently nearly as dead as LSB, we can only ignore it
if we don't want to stop and kill all innovation."

libexec/pyenv

@@ -94,7 +94,7 @@ if [ "${bin_path%/*}" != "$PYENV_ROOT" ]; then
   # Add pyenv's own `pyenv.d` unless pyenv was cloned to PYENV_ROOT
   PYENV_HOOK_PATH="${PYENV_HOOK_PATH}:${bin_path%/*}/pyenv.d"
 fi
-PYENV_HOOK_PATH="${PYENV_HOOK_PATH}:/usr/local/etc/pyenv.d:/etc/pyenv.d:/usr/lib/pyenv/hooks"
+PYENV_HOOK_PATH="${PYENV_HOOK_PATH}:/usr/etc/pyenv.d:/usr/local/etc/pyenv.d:/etc/pyenv.d:/usr/lib/pyenv/hooks"
 for plugin_hook in "${PYENV_ROOT}/plugins/"*/etc/pyenv.d; do
   PYENV_HOOK_PATH="${PYENV_HOOK_PATH}:${plugin_hook}"
 done