"Transaction ... is no longer running" after user sends invalid data.

Tested on: stable/beryllium
Caught by: Netconf MDSAL Northbound suite

After user sends invalid data to the "modules" node of ODL's NETCONF configutation and after that request errors out (uncleanly, see NETCONF-132), all other operations in that session fail with

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<rpc-reply message-id="6" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>operation-failed</error-tag>
<error-severity>error</error-severity>
<error-message>Unexpected error</error-message>
<error-info>
<error>java.lang.IllegalStateException: Transaction DOM-31 is no longer running</error>
</error-info>
</rpc-error>
</rpc-reply>

(the "DOM-31" in the <error> element can vary).