Add recovery service.

RecoverySystemService is separated from PowerManagerService as a
dedicated system service to handle recovery related requests (such as
invoking uncrypt to uncrypt an OTA package on /data or to set up /
clear the bootloader control block (i.e. /misc) and etc).

The matching CL in frameworks/base is in:
  Change-Id: Ic606fcf5b31c54ce54f0ab12c1768fef0fa64560.

Bug: 26830925
Change-Id: Iee0583c458f784bfa422d0f7af5d1f2681d9609e
(cherry picked from commit 65b5fde912285ebeeefc9c7486f4453dd86d994f)
diff --git a/service_contexts b/service_contexts
index 39e004c..dfd7404 100644
--- a/service_contexts
+++ b/service_contexts
@@ -101,6 +101,7 @@
 radio.phonesubinfo                        u:object_r:radio_service:s0
 radio.phone                               u:object_r:radio_service:s0
 radio.sms                                 u:object_r:radio_service:s0
+recovery                                  u:object_r:recovery_service:s0
 restrictions                              u:object_r:restrictions_service:s0
 rttmanager                                u:object_r:rttmanager_service:s0
 samplingprofiler                          u:object_r:samplingprofiler_service:s0