Fixed when SystemServerInitThreadPool.shutdown() is called.

The class' Javadoc says it's shut down after P HASE_BOOT_COMPLETED, whic was
not the case.

Test: manual verification / boot
Fixes: 156257347

Change-Id: I3c8b24c6855c7c83cdf1eacc637b8e064a121fe3

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

@@ -590,7 +590,6 @@ public final class SystemServer {
             startBootstrapServices(t);
             startCoreServices(t);
             startOtherServices(t);
-            SystemServerInitThreadPool.shutdown();
         } catch (Throwable ex) {
             Slog.e("System", "******************************************");
             Slog.e("System", "************ Failure starting system services", ex);