Starting the subsystem consists of firing an event
to the subsystem poller's lcore and performing
I/O channel initialization (for virtual NVMe
subsystems) before starting the poller.
Previously the subsystem would be started immediately
when created, which was before the subsystem's
mode and other parameters (such as a virtual subsystem's
bdevs) have been set. This resulted in no I/O channels
being allocated in virtual subsystem mode.
So break out the start code into a new
nvmf_tgt_start_subsystem() function, which clients
must call after fully initializing a subsystem created
with nvmf_tgt_create_subsystem().
Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I56534668887ef99d2e892844acd12194920c3245