crimson/osd/object_context_loader: cleanup with_clone_obc_direct

crimson/osd/object_context_loader: cleanup with_clone_obc_direct

ObjectContextLoader interface provides two variants:

* with_obc:
  // Use this variant by default
  // If oid is a clone object, the clone obc *and* it's
  // matching head obc will be locked and can be used in func.

* with_clone_obc_only:
  // Use this variant in the case where the head object
  // obc is already locked and only the clone obc is needed.
  // Avoid nesting with_head_obc() calls by using with_clone_obc()
  // with an already locked head.

with_clone_obc_direct variant is equal to with_obc on a clone obc
since both the head and the clone obcs will be locked and can be used.

Signed-off-by: Matan Breizman <mbreizma@redhat.com>