Refactor: libcib: Use cib_operation_t in cib_file.c

This way we can add support for transactions without adding another
boolean to cib_func_entry. This also facilitates merging cib_server_ops
and cib_file_ops in the future, if we think of a nice way to handle
differing fn members.

Ref T185

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>