Fixed wrong error message when no PFs are found.

    Also added unit-tests

Issue: 332710

Change-Id: I0c874c51b82e9823d50af67e544c5599e2068bc0
Signed-off-by: Roey Chen <roeyc@mellanox.com>
Fixed eswitchd logging

Using logging.basicConfig, log will be written to the file
configured under 'log_file' in the [DEFAULT] section of `eswitchd.conf`
Log level is set to DEBUG

Issue: 332710

Change-Id: I7aad667ad1a28748a3511ae399c6afeebc2d5fc5
Signed-off-by: Roey Chen <roeyc@mellanox.com>