Issue similar to NETCONF-382, but applies to leafrefs.

Restconf is using global schema context to deserialize external leafrefs.

For URLs such as:

/restconf/config/network-topology:network-topology/topology/topology-netconf/node/vpp/yang-ext:mount/openconfig-network-instance:network-instances/network-instance/global-bgp

where global-bgp is leafref and openconfig-network-instance is not present in global schema context,

restconf fails with error:

java.lang.IllegalArgumentException: Module reference cannot be NULL

    at com.google.common.base.Preconditions.checkArgument(Preconditions.java:134)
    at org.opendaylight.yangtools.yang.model.util.SchemaContextUtil.findDataSchemaNode(SchemaContextUtil.java:125)
    at org.opendaylight.yangtools.yang.model.util.SchemaContextUtil.getBaseTypeForLeafRef(SchemaContextUtil.java:659)
    at org.opendaylight.netconf.sal.restconf.impl.ControllerContext.addKeyValue(ControllerContext.java:771)