[telemetry] Fix MSR CanMonitorPower().

Ah, the dangers of dynamic typing and implicit type conversion.
Typo in https://codereview.chromium.org/577893003

BUG=336556, 336558
TEST=None.
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/605633002

Cr-Commit-Position: refs/heads/master@{#296657}

tools/telemetry/telemetry/core/platform/platform_backend_unittest.py

@@ -13,7 +13,9 @@ class PlatformBackendTest(unittest.TestCase):
   def testPowerMonitoringSync(self):
     # Tests that the act of monitoring power doesn't blow up.
     platform = platform_module.GetHostPlatform()
-    if not platform.CanMonitorPower():
+    can_monitor_power = platform.CanMonitorPower()
+    self.assertIsInstance(can_monitor_power, bool)
+    if not can_monitor_power:
       logging.warning('Test not supported on this platform.')
       return
 

tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py

@@ -123,6 +123,7 @@ class MsrPowerMonitor(power_monitor.PowerMonitor):
     except OSError as e:
       logging.info('Cannot monitor power: %s' % e)
       return False
+    return True
 
   def _WinCanMonitorPower(self):
     family, model = map(int, re.match('.+ Family ([0-9]+) Model ([0-9]+)',