core: Not able to push more than one external...

Not able to push more than one external event in 30 second using REST API

This patch enables to add external events with flood rate below 30 if
specified in the POST message.
For example :
<event>
        <description>1</description>
        <severity>normal</severity>
        <origin>CUSTOMER1</origin>
        <custom_id>1</custom_id>
        <flood_rate>1</flood_rate>
</event>

if the following is sent:

<event>
        <description>1</description>
        <severity>normal</severity>
        <origin>CUSTOMER1</origin>
        <custom_id>1</custom_id>
</event>

a default flood rate of 30 sec is used.

Change-Id: I91526e2a744cc6de413091fd1605bf7f08c46735
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1071840
Signed-off-by: Eli Mesika <emesika@redhat.com>