Steps to follow,

1. Add a flow

PUT http://localhost:8080/controller/nb/v2/flowprogrammer/default/node/MD_SAL/openflow:1/staticFlow/flow109

<flowConfig>
<installInHw>true</installInHw>
<name>flow109</name>
<node>
<id>openflow:1</id>
<type>MD_SAL</type>
</node>
<ingressPort>openflow:1:1</ingressPort>
<priority>5109</priority>
<etherType>0x800</etherType>
<nwSrc>9.9.1.2</nwSrc>
<actions>OUTPUT=openflow:1:1</actions>
</flowConfig>

2. Update the flow

<flowConfig>
<installInHw>true</installInHw>
<name>flow109</name>
<node>
<id>openflow:1</id>
<type>MD_SAL</type>
</node>
<ingressPort>openflow:1:1</ingressPort>
<priority>5109</priority>
<etherType>0x800</etherType>
<nwSrc>9.9.1.3</nwSrc>
<actions>OUTPUT=openflow:1:1</actions>
</flowConfig>

3. Check with RESTCONF

http://localhost:8080/restconf/config/opendaylight-inventory:nodes/node/openflow:1/table/0/flow/0

The flow should have been updated

4. Now check on the switch

sudo ovs-ofctl -O OpenFlow13 dump-flows s1

You will see this,

OFPST_FLOW reply (OF1.3) (xid=0x2):
cookie=0x0, duration=477.033s, table=0, n_packets=0, n_bytes=0, send_flow_rem priority=5109,ip,in_port=1,nw_src=9.9.1.2 actions=output:1

when you expect to see this

OFPST_FLOW reply (OF1.3) (xid=0x2):
cookie=0x0, duration=477.033s, table=0, n_packets=0, n_bytes=0, send_flow_rem priority=5109,ip,in_port=1,nw_src=9.9.1.3 actions=output:1

Note that for this example I used the FlowProgrammer NB API but I would expect to see similar results when using RESTCONF or the CLI to add the flow.