Fixes show commands failure when database is not ready

[Kalimuthu-Velappan]

Change-Id: I3857bd80ab9667f5f2bd93496d0205eb97962246

- What I did
Fixes show commands failure when the database is not ready:

When interface show commands are executed before database service ready, it throws a connection error.

- How I did it

Added try..catch block for the database connection object.

    try:
        config_db = ConfigDBConnector()
         config_db.connect()
    except Exception as e:
         click.echo("Database service is not ready!\n")
        sys.exit(0)

- How to verify it

 Run the show command when the database is not ready.

- Previous command output (if the output of a command-line utility has changed)

- New command output (if the output of a command-line utility has changed)

-->

[Kalimuthu-Velappan]

Removed the redundant print statement

[jleveque]

Remove space between echo and opening parenthesis.

[jleveque]

Can you provide a more specific Exception(s) here?

[Kalimuthu-Velappan]

will add it