Call InitPartitionMetadata when resuming an update.

BootControlAndroid::InitPartitionMetadata() should always be called when
starting / resuming an update that uses dynamic partitions. This allows
updating the metadata for the target slot, as well as setting up the
internal state for accessing the dynamic partitions in the target slot.

Bug: 122097567
Test: Run update_engine_unittests on taimen and blueline.
Test: Apply a payload that uses dynamic partitions. Reboot before it
      finishes, then resume the update.
Change-Id: I1353f7460a61c0183654b6349689beaa9bf12129
diff --git a/common/constants.cc b/common/constants.cc
index 3ae7a60..310f1b2 100644
--- a/common/constants.cc
+++ b/common/constants.cc
@@ -37,8 +37,8 @@
 const char kPrefsDailyMetricsLastReportedAt[] =
     "daily-metrics-last-reported-at";
 const char kPrefsDeltaUpdateFailures[] = "delta-update-failures";
-const char kPrefsDynamicPartitionMetadataInitialized[] =
-    "dynamic-partition-metadata-initialized";
+const char kPrefsDynamicPartitionMetadataUpdated[] =
+    "dynamic-partition-metadata-updated";
 const char kPrefsFullPayloadAttemptNumber[] = "full-payload-attempt-number";
 const char kPrefsInstallDateDays[] = "install-date-days";
 const char kPrefsLastActivePingDay[] = "last-active-ping-day";