REF_DEBUG: Install refcounter.py to $(ASTDATADIR)/scripts

This change ensures refcounter.py is installed to a place where it
can be found by the Asterisk testsuite if REF_DEBUG is enabled.

ASTERISK-24432 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4094/
........

Merged revisions 426830 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@426831 f38db490-d61c-443f-a65b-d21fe96a405b