Bulk creation of VM's are failed. Some of VM instances cannot acquire IP,observed when instance count goes beyond 15

ODL Version : distribution-karaf-0.5.2-Boron-SR2

Openstack Version : mitaka

Setup Details : 3 ODL Nodes + 1 Control Node + 2 Compute Nodes

Steps to Reproduce:
1. Start ./karaf and install odl-ovsdb-openstack and jolokia bundle.
2. Check cluster is formed. And check network topology is initiated.
3. ./stack the Control and Compute nodes. And verify initial flows.
4. Create a network
5. Create 20 Instances for the network

Observation:
Maximum for the first 15 Instances IP address is been assigned. Thereafter IP address for the remaining Instances is not assigned.

Note:
The above observation is not observed when we do set-manager and del-manager manager for the OVS nodes.

Please find the attached files for karaf logs.