Fix: sink.ctf.fs: possible uses after free because of unchecked return values

Fix: sink.ctf.fs: possible uses after free because of unchecked return values

Uses after free are possible because we ignore the return value of the
`bt_ctfser_write_*()` function calls. To avoid this, check the return
values and log an error message.

  CID 1401217 (#4 of 4): Use after free (USE_AFTER_FREE)
  11. deref_arg: Calling bt_ctfser_write_byte_aligned_unsigned_int
  dereferences freed pointer stream->ctfser.base_mma

  CID 1401193 (#2 of 2): Unchecked return value (CHECKED_RETURN)
  8. check_return: Calling bt_ctfser_write_byte_aligned_unsigned_int
  without checking return value (as is done elsewhere 8 out of 10
  times).

Reported-by: Coverity (1401217) Use after free
Reported-by: Coverity (1401193) Unchecked return value
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I7581c0e549d7bf916f42afe306976baa9822897a
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1286
Tested-by: jenkins
Reviewed-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>