Serialize the config objects

This commit serializes the config object into cereal
path and restores the config object when the phosphor-ldap-conf
restarts.

TestedBy: Unit tested
          Serialize the object
          Restart the phosphor-ldap-conf restores the object.
          Ldap/Local authentication works fine.

Signed-off-by: Ratan Gupta <ratagupt@linux.vnet.ibm.com>
Change-Id: Ie6e940ddd6851085dc4213677dfb20e3afa0964f
11 files changed