power_LoadTest: prefix PSR residency keyval with percent.

BUG=chrome-os-partner:53976
TEST=none

Change-Id: I415e3228419e67c2da4e8c65fb42ac5265f27802
Reviewed-on: https://chromium-review.googlesource.com/349660
Commit-Ready: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
diff --git a/client/site_tests/power_LoadTest/power_LoadTest.py b/client/site_tests/power_LoadTest/power_LoadTest.py
index 989488d..599fb6d 100755
--- a/client/site_tests/power_LoadTest/power_LoadTest.py
+++ b/client/site_tests/power_LoadTest/power_LoadTest.py
@@ -292,7 +292,7 @@
         t1 = time.time()
         self._tmp_keyvals['minutes_battery_life_tested'] = (t1 - t0) / 60
         if psr_t0:
-            self._tmp_keyvals['psr_residency'] = \
+            self._tmp_keyvals['percent_psr_residency'] = \
                 (self._get_psr_counter() - psr_t0) / (10 * (t1 - t0))