As part of overall NETVIRT-719 Karaf 4 testing, and after OPNFLWJAVA-84 seems to have been fixed (thanks), I'm seeing this in the log during a shutdown (so not blocking):

2017-06-13 16:37:56,803 | WARN | Framework stop | SwitchConnectionProviderImpl | 329 - org.opendaylight.openflowjava.openflow-protocol-impl - 0.10.0.SNAPSHOT | Can not shutdown - not configured or started

2017-06-13 16:37:56,804 | ERROR | Framework stop | BeanRecipe | 11 - org.apache.aries.blueprint.core - 1.7.1 | The blueprint bean openflowPluginProvider in bundle org.opendaylight.openflowplugin.blueprint-config/0.5.0.SNAPSHOT incorrectly threw an exception from its destroy method.
java.lang.IllegalStateException: SwitchConnectionProvider is not started or not configured.
at org.opendaylight.openflowjava.protocol.impl.core.SwitchConnectionProviderImpl.shutdown(SwitchConnectionProviderImpl.java:102)
at Proxyf638eb93_0978_401f_8584_1ce5049c39b9.shutdown(Unknown Source)
at Proxyc5d0aa77_ccd2_4e71_b117_35e56dde2f14.shutdown(Unknown Source)
at org.opendaylight.openflowplugin.impl.OpenFlowPluginProviderImpl.lambda$shutdownSwitchConnections$1(OpenFlowPluginProviderImpl.java:176)
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)[:1.8.0_131]
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)[:1.8.0_131]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)[:1.8.0_131]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)[:1.8.0_131]
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)[:1.8.0_131]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)[:1.8.0_131]
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)[:1.8.0_131]
at org.opendaylight.openflowplugin.impl.OpenFlowPluginProviderImpl.shutdownSwitchConnections(OpenFlowPluginProviderImpl.java:177)
at org.opendaylight.openflowplugin.impl.OpenFlowPluginProviderImpl.close(OpenFlowPluginProviderImpl.java:502)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)[:1.8.0_131]