Assume UNSUPPORTED if the battery capacity level sysfs node does
not exist.

Bug: 163382088
Test: Ensure that, if the ./capacity_level does not exist,
  that the device will shut down at 0 % SOC in an Health 2.1
  implementation
Change-Id: I00822b4bfba5d823c1a30163ea6824e59d3aae32
diff --git a/healthd/BatteryMonitor.cpp b/healthd/BatteryMonitor.cpp
index 599f500..fd810cb 100644
--- a/healthd/BatteryMonitor.cpp
+++ b/healthd/BatteryMonitor.cpp
@@ -79,7 +79,7 @@
 
     // HIDL enum values are zero initialized, so they need to be initialized
     // properly.
-    health_info_2_1->batteryCapacityLevel = BatteryCapacityLevel::UNKNOWN;
+    health_info_2_1->batteryCapacityLevel = BatteryCapacityLevel::UNSUPPORTED;
     health_info_2_1->batteryChargeTimeToFullNowSeconds =
             (int64_t)Constants::BATTERY_CHARGE_TIME_TO_FULL_NOW_SECONDS_UNSUPPORTED;
     auto* props = &health_info_2_1->legacy.legacy;