Allow 'ip addr flush' to loop more than 10 times

Allow 'ip addr flush' to loop more than 10 times

The default remains at 10 for backwards compatibility.

For instance:
 # ip addr flush dev eth2
 *** Flush remains incomplete after 10 rounds. ***
 # ip -l 20 addr flush dev eth2
 *** Flush remains incomplete after 20 rounds. ***
 # ip -loops 0 addr flush dev eth2
 #

This is useful for getting rid of large numbers of IP
addresses in scripts.

Signed-off-by: Ben Greear <greearb@candelatech.com>