[2480] add srcdir/src/lib/python to PYTHONPATH; needed for isc.dns.

src/bin/loadzone/run_loadzone.sh.in

@@ -18,7 +18,7 @@
 PYTHON_EXEC=${PYTHON_EXEC:-@PYTHON@}
 export PYTHON_EXEC
 
-PYTHONPATH=@abs_top_builddir@/src/lib/python/isc/log_messages:@abs_top_builddir@/src/lib/python:@abs_top_builddir@/src/lib/dns/python/.libs
+PYTHONPATH=@abs_top_builddir@/src/lib/python/isc/log_messages:@abs_top_builddir@/src/lib/python:@abs_top_srcdir@/src/lib/python:@abs_top_builddir@/src/lib/dns/python/.libs
 export PYTHONPATH
 
 # If necessary (rare cases), explicitly specify paths to dynamic libraries