[1976] Fix distcheck

A file was not cleaned.

src/bin/cfgmgr/plugins/Makefile.am

@@ -11,7 +11,7 @@ config_plugin_DATA = logging.spec tsig_keys.spec datasrc.spec
 python_PYTHON = b10logging.py tsig_keys.py datasrc_config_plugin.py
 pythondir = $(config_plugindir)
 
-CLEANFILES = b10logging.pyc tsig_keys.pyc
+CLEANFILES = b10logging.pyc tsig_keys.pyc datasrc.spec
 CLEANDIRS = __pycache__
 
 clean-local: