Add type property to HealthMonitor in the CLI

This patch adds the missing type property which causes the Bad Request
errors when the new health monitors are posted.

This fixes MN-1582.

Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Merge pull request #142 from tfukushima/l4lb-hm-fix-master

Add type property to HealthMonitor in the CLI