nvme: fix pci device leak when detaching a controller in primary process

This case isn't particularly supported, but still
caused a memory leak and rendered the pci device
inaccessible for the rest of the primary process
lifetime.

This happens when a controller is removed from the
primary process while a secondary process still
uses it. The controller will likely misbehave without
its primary process managing it, but at least there
won't be a leak.

Change-Id: I67581cffa33ce14ff516b5743d13c9ef7b351625
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/434408


Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>