allow watchdog to dump servicemanager

Cmd line: /system/bin/servicemanager
ABI: 'x86_64'

"servicemanager" sysTid=202
  NOTE: Function names and BuildId information is missing for some frames due
  NOTE: to unreadable libraries. For unwinds of apps, only shared libraries
  NOTE: found under the lib/ directory are readable.
  NOTE: On this device, run setenforce 0 to make the libraries readable.
  NOTE: Unreadable libraries:
  NOTE:   /system/lib64/bootstrap/libc.so
    #00 pc 00000000000babda  /system/lib64/bootstrap/libc.so
    #01 pc 0000000000017819  /system/lib64/libutils.so (android::Looper::pollAll(int, int*, int*, void**)+441) (BuildId: 2ed0ced7383d1676a37aed1236486ac3)
    #02 pc 0000000000011a25  /system/bin/servicemanager (main+1157) (BuildId: 509b83cb97addfa90aaa4ad911c2a3df)
    #03 pc 00000000000547a9  /system/lib64/bootstrap/libc.so

Bug: 314088872
Test: adb shell am hang and check ANRs
Change-Id: I7daf19a3afbd18aa93093fb152f9555022ece88f
diff --git a/private/system_server.te b/private/system_server.te
index 8c26cc7..2ecc0a5 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -388,6 +388,7 @@
   mediatuner
   netd
   sdcardd
+  servicemanager
   statsd
   surfaceflinger
   vold