Fix several bugs in nclprovisioner capability and ncl provisioner tests.

NCLProvisionerCapability:

- If SLA Manager information did not exists, it launches a capability exception. This capability exception was caught  by the Resource when starting its capabilities, and the capability was shut down. But NCLProvisioner capability should work even when there's no need to push information to SLA.

- Solve nullpointers regarding SLA notification and event listener when they're not initialized (nullpointer resided in deactivate method, which assumed they are not null -> they were initialized)

NCLProvisionerTest

- Mock sdnNotification client with powermockito.