Fix debug object on stack warning

Fix debug object on stack warning

When running the SPLAT tests on a kernel with CONFIG_DEBUG_OBJECTS=y
enabled the following warning is generated.

  ODEBUG: object is on stack, but not annotated
  WARNING: at lib/debugobjects.c:300 __debug_object_init+0x221/0x480()

This is caused by the test cases placing a debug object on the stack
rather than the heap.  This isn't harmful since they are small objects
but to make CONFIG_DEBUG_OBJECTS=y happy the objects have been relocated
to the heap.  This impacted taskq tests 1, 3, and 7.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #424