Add missing close in sending uidMap

Add missing close call to write side of the uid map pipe. More context
in b/286471361.

Test: verified with traces that informAllUidData no longer blocks
Test: builds, boots
Bug: 286471361
Ignore-AOSP-First: needed in UDC
Change-Id: I875027722aba1d681b0b0cd5c210761e81da6e4c
diff --git a/service/java/com/android/server/stats/StatsCompanionService.java b/service/java/com/android/server/stats/StatsCompanionService.java
index fd987c2..367bfdd 100644
--- a/service/java/com/android/server/stats/StatsCompanionService.java
+++ b/service/java/com/android/server/stats/StatsCompanionService.java
@@ -279,6 +279,7 @@
                 }
             } finally {
                 if (DEBUG) Log.d(TAG, "End thread for sending uid map data.");
+                FileUtils.closeQuietly(fout);
                 backgroundThread.quit();
             }
         });