[cmyth] Remove cmyth_mysql_get_commbreaklist

This commit removes the functions cmyth_mysql_get_commbreaklist,
cmyth_mysql_query_commbreak_count and cmyth_mysql_query_commbreak_list.

As a replacement, cmyth_get_commbreaklist should be used.

Reasons for removing cmyth_mysql_query_commbreak_list:
- Memory leaks and dereferencing null pointer in case when an incorrect
  dataset is received
- Different implementations based on protocol version, should use db
  schema version instead
- Slow algorithm