ceph plugin: Rewrite parse_keys() and compact_ds_name().

ceph plugin: Rewrite parse_keys() and compact_ds_name().

This rewrite removes the logic to add the original length to the end of
the buffer in case of truncation. This logic was guarded by:
  tmp[DATA_MAX_NAME_LEN - 1] = '\0';
  if(strlen(tmp) > DATA_MAX_NAME_LEN - 1) { ... }
and was therefore dead code.

Fixes: #1350