Description of problem:
If I press on OK rapidly when creating a network through the Network tab, the network is created multiply times


Steps to Reproduce:
1. In the network tab, create new network
2. Select any name (length < 15) (for example: 'networkName')
3. Select any Data Center
4. Click rapidly on OK.

Actual results:
The network 'networkName' will be created several time.

Expected results:
The network 'networkName' should be created once.

Additional info:
After the rapid clicking, the following message pop:
"Error while executing action: Cannot add Network. The logical network's name is 
 already used by an existing logical network in the same data-center.
 -Please choose a different name."
(The networks are still being created)