Change the nslcd configuration based on CertificateString Property

- When ever replace client certificate method is called by the
  certificate manager, it sends out a PropertyChange Signal which
  will be captured by the phosphor-user-manager and inturn it re-writes
  the configuration & restarts nslcd accordingly.

- The idea of this commit is to only consider the Property change on
  CertificateString Property and write the configuration and not consider
  the change in any other property under the same Interface.

TestedBy:
Tried replacing a new client certificate using bustcl call, and verified
that we write the configuration only when the CertificateString Property
is changed.

Signed-off-by: manojkiraneda <manojkiran.eda@gmail.com>
Change-Id: Id1392365127807d2069c391b8ccc2c4c0a9b7215
1 file changed