openldap: fix QA Warning

While building openldap, there was a warning, like below:

WARNING: QA Issue: openldap: Files/directories were installed but not shipped in any package:
  /usr/libexec
Please set FILES such that these items are packaged. Alternatively if they are unneeded, avoid installing them or delete them within do_install.
openldap: 1 installed and not shipped files. [installed-vs-shipped]

This is because that after openldap all contents of /usr/libexec are split
into subsets or moved into other directory and no one makes use of it.

So, to fix this QA warning, delete /usr/libexec.

Signed-off-by: Qi Hou <qi.hou@windriver.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
(cherry picked from commit aaf496df4c)
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-oe/recipes-support/openldap/openldap_2.4.45.bb

@@ -188,6 +188,7 @@ do_install_append() {
 
     # Installing slapd under ${sbin} is more FHS and LSB compliance
     mv ${D}${libexecdir}/slapd ${D}/${sbindir}/slapd
+    rmdir --ignore-fail-on-non-empty ${D}${libexecdir}
     SLAPTOOLS="slapadd slapcat slapdn slapindex slappasswd slaptest slapauth slapacl slapschema"
     cd ${D}/${sbindir}/
     rm -f ${SLAPTOOLS}