ldap: Add distro feature for LDAP

LDAP related packages will be pulled into the
image depending on the distro feature.

Enabling this feature increases the image size by ~500KB
as it brings nss-pam-ldapd, openldap, and nscd into the image.

Change-Id: Ia11e7574b69056de4221fd66c022dbe8e5641d1e
Signed-off-by: Ratan Gupta <ratagupt@in.ibm.com>
diff --git a/conf/distro/include/phosphor-base.inc b/conf/distro/include/phosphor-base.inc
index 3947f36..24ce8dc 100644
--- a/conf/distro/include/phosphor-base.inc
+++ b/conf/distro/include/phosphor-base.inc
@@ -117,6 +117,7 @@
         pam \
         slp \
         systemd \
+        ldap \
         "
 
 DISTRO_FEATURES = " \