lib/azure_blob_req: validate az_req_* arguments
lib/azure_blob_req: validate az_req_* arguments

Belt and braces checks for NULL account, container, blob or _op
pointers.

Signed-off-by: David Disseldorp <589a549dc9f982d9f46aeeb82a09ab6d87ccf1d8@suse.de>

ddiss/elasto,ddiss/elasto