storage: Introduce storagePoolUpdateAllState function

storage: Introduce storagePoolUpdateAllState function

The 'checkPool' callback was originally part of the storageDriverAutostart function,
but the pools need to be checked earlier during initialization phase,
otherwise we can't start a domain which mounts a volume after the
libvirtd daemon restarted. This is because qemuProcessReconnect is called
earlier than storageDriverAutostart. Therefore the 'checkPool' logic has been
moved to storagePoolUpdateAllState which is called inside storageDriverInitialize.

We also need a valid 'conn' reference to be able to execute 'refreshPool'
during initialization phase. Though it isn't available until storageDriverAutostart
all of our storage backends do ignore 'conn' pointer, except for RBD,
but RBD doesn't support 'checkPool' callback, so it's safe to pass
conn = NULL in this case.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1177733