perf trace: Use $PERF_EXEC_PATH in canned report scripts

Set $PERF_EXEC_PATH before starting the record and report scripts, and
make them use it where necessary.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286723403.2955.205.camel@localhost>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/scripts/python/bin/netdev-times-report b/tools/perf/scripts/python/bin/netdev-times-report
index c3d0a63..4ad361b 100644
--- a/tools/perf/scripts/python/bin/netdev-times-report
+++ b/tools/perf/scripts/python/bin/netdev-times-report
@@ -2,4 +2,4 @@
 # description: display a process of packet and processing time
 # args: [tx] [rx] [dev=] [debug]
 
-perf trace -s ~/libexec/perf-core/scripts/python/netdev-times.py $@
+perf trace -s "$PERF_EXEC_PATH"/scripts/python/netdev-times.py $@