Fix path to mlock_report

This patch fixes path to mlock_report.py. Also add python-psutil
to dstat depends as it is required by mlock_report.

Change-Id: Ia2b507a7b923f1e3393a9cb7746c66d39d6abfde
diff --git a/tools/memory_tracker.sh b/tools/memory_tracker.sh
index cbdeb8f..63f25ca 100755
--- a/tools/memory_tracker.sh
+++ b/tools/memory_tracker.sh
@@ -88,7 +88,7 @@
             # list processes that lock memory from swap
             if [[ $unevictable -ne $unevictable_point ]]; then
                 unevictable_point=$unevictable
-                ${PYTHON} ./tools/mlock_report.py
+                ${PYTHON} $(dirname $0)/mlock_report.py
             fi
 
             echo "]]]"