osdc/Objecter: invalidate crcs on preallocated rx buffers

osdc/Objecter: invalidate crcs on preallocated rx buffers

Both simple and async messengers use c_str() when copying the data from
the socket into the receive buffer, going behind bufferlist's back.  If
the receive buffer is preallocated, we need to invalidate its crc cache
by hand to avoid possible data crc mismatches on the client side.

Fixes: https://tracker.ceph.com/issues/38416
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 3eeab975b604d9fc4290747f85a78d59a2452c2e)

Conflicts:
	src/test/librados/io_cxx.cc
- In master, 3730d10623650ce8569be96b28cbba599a9a0db6 renamed this file from
  src/test/librados/io.cc but that commit is not being backported to luminous.
  Manually cherry-picked the test mods into src/test/librados/io.cc.