ODL Controller is unable to insert flows in OVS - flows are missing in T21

Overview:
---------
ODL Controller is unable to insert flows in OVS - flows are missing in T21

Details:
--------

• Loaded a setup with cluster of ODL controllers (3)
• Created 3 + external network
• 1 router connected to all networks
• 6 VMs (2 per network)

Observed behavior:
------------------

• Only one VM had connectivity to FIP
• No L3 connectivity between the VMs

Investigation (with Olga S. Help):
----------------------------------
it seems to be an issue while installing rules to the OVS. I have looked at the devstack-newton-2: ip/10.0.107.147, NodeId:Uri [_value=openflow:35570990444905]

In the karaf odl1.log , I can see multiple errors like below. It happens each time when FIB entry should be installed to OVS:
2017-04-03 14:12:23,271 | ERROR | CommitFutures-10 | MDSALManager | 338 - org.opendaylight.genius.mdsalutil-impl - 0.1.3.R1_0-SR2_1 | Install Flow – Failed because of concurrent transaction modifying same data

Therefore in OVS dump-flows the rules are missed, but they exist in the inventory-nodes DS model .
For example, you can look for L3.35570990444905.21.1b659968-a509-4645-9cb3-6532031c242e.42.2.2.2.212 here :
http://10.0.97.46:8181/restconf/config/opendaylight-inventory:nodes

<flow>
<id>L3.35570990444905.21.1b659968-a509-4645-9cb3-6532031c242e.42.2.2.2.212</id>
<hard-timeout>0</hard-timeout>
<idle-timeout>0</idle-timeout>
<match>
<ethernet-match>
<ethernet-type>
<type>2048</type>
</ethernet-type>
</ethernet-match>
<metadata>
<metadata>140002</metadata>
<metadata-mask>4294967294</metadata-mask>
</metadata>
<ipv4-destination>2.2.2.212/32</ipv4-destination>
</match>
<cookie>134217731</cookie>
<instructions>
<instruction>
<order>0</order>
<apply-actions>
<action>
<order>0</order>
<group-action>
<group-id>150005</group-id>
</group-action>
</action>
</apply-actions>
</instruction>
</instructions>
<installHw>true</installHw>
<barrier>false</barrier>
<strict>false</strict>
<priority>42</priority>
<table_id>21</table_id>
<flow-name>
L3.35570990444905.21.1b659968-a509-4645-9cb3-6532031c242e.42.2.2.2.212
</flow-name>
</flow>