Duplicate dns host-record with same hostname and ip are getting created

[Joseph Vazhappilly]

Brief Description
-----------------
System CLI allows to create multiple host records with same dns name and ip address successfully without error

Severity
--------
Minor

Steps to Reproduce
------------------
1. Login to system
2. Create multiple dns host with the same dns name and ip address
3. Observed that the duplicate host records are getting created without any issue
4. For Example:
    system service-parameter-add dns host-record samename1=host,1.1.1.1
    system service-parameter-add dns host-record samename2=host,1.1.1.1

Expected Behavior
------------------
DNS host record with same name and ip should not be allowed. If user is trying to create, error should be thrown that it is already present

Actual Behavior
----------------
Creation of duplicate host records is successful

Reproducibility
---------------
100%

System Configuration
--------------------
One node system

Branch/Pull Time/Commit
-----------------------
starlingx/master

Last Pass
---------
NA

Timestamp/Logs
--------------
NA

Test Activity
-------------
Feature Testing

Workaround
----------
NA

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/config/+/903493
Committed: https://opendev.org/starlingx/config/commit/f586a97eadc62cbc63f9c1bc521ca76311361774
Submitter: "Zuul (22348)"
Branch: master

commit f586a97eadc62cbc63f9c1bc521ca76311361774
Author: Joseph Vazhappilly <email address hidden>
Date: Tue Dec 12 00:10:55 2023 -0500

    Check duplicate in host-record service parameter

    This change restricts user to create dns host-record with same value
    A check is added to validate host-record value against already existing
    values before create or modify operations.

    Closes-bug: 2046247

    Test Plan:
    PASS: Verify build and install
    PASS: Verify service-parameter-add to add duplicate host-record
    PASS: Verify service-parameter-modify with existing host-record

    Change-Id: Ic58e863a8c1715e1237edee1f69573af4bbdb939
    Signed-off-by: Joseph Vazhappilly <email address hidden>