Remove dead code from SystemServer

Remove dead code from SystemServer that obstensively protects devices
from negative (< 1970) system clock times, but does not.

In reality, SystemServer calls SystemClock.setCurrentTimeMillis(), which
calls through to the AlarmManager.setTime() binder call. When the code
runs the system server hasn't started any services yet, so this would
always fail.

AlarmManager has similar protections in place that do work: if the
device is earlier than a "build time", then the device's clock is forced
forward. That provides the protection that the code being removed from
SystemServer was trying to achieve.

Test: Added logging to SystemClock to prove AlarmManager is null /
manual debugging

Change-Id: I87dca1062829bc1a10202804fa7ee31e0a6f03a3

core/java/android/os/SystemClock.java

@@ -154,6 +154,7 @@ public final class SystemClock {
         final IAlarmManager mgr = IAlarmManager.Stub
                 .asInterface(ServiceManager.getService(Context.ALARM_SERVICE));
         if (mgr == null) {
+            Slog.e(TAG, "Unable to set RTC: mgr == null");
             return false;
         }
 

services/java/com/android/server/SystemServer.java

@@ -383,15 +383,6 @@ public final class SystemServer {
             EventLog.writeEvent(EventLogTags.SYSTEM_SERVER_START,
                     mStartCount, mRuntimeStartUptime, mRuntimeStartElapsedTime);
 
-            // If a device's clock is before 1970 (before 0), a lot of
-            // APIs crash dealing with negative numbers, notably
-            // java.io.File#setLastModified, so instead we fake it and
-            // hope that time from cell towers or NTP fixes it shortly.
-            if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
-                Slog.w(TAG, "System clock is before 1970; setting to 1970.");
-                SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
-            }
-
             //
             // Default the timezone property to GMT if not set.
             //