logd: validate and fill in socket credentials

- android::pidToUid() additional checking.  Make sure if we have to
  convert a PID to an UID that the parse of /proc/<pid>/status
  requires a trailing space after the number
- android::tidToPid() added, in the same vein as android::pidToUid().
- stats.tidToPid() added
- If no credentials, set PID to 0 and UID to DEFAULT_OVERFLOWUID
- If credentialed PID is 0, use stats.tidToPid()
- If credentialed UID is DEFAULT_OVERFLOWUID, use stats.pidToUid()

Test: remove +passcred from logd.rc for daemon and confirm very few
      UID=65534 or PID=0 cases actually show up
Bug: 37985222
Change-Id: I7d20506e70e67beb3043d1537cf9450ab58dc278
diff --git a/logd/LogBufferInterface.cpp b/logd/LogBufferInterface.cpp
index 3cb2b89..4b6d363 100644
--- a/logd/LogBufferInterface.cpp
+++ b/logd/LogBufferInterface.cpp
@@ -15,8 +15,15 @@
  */
 
 #include "LogBufferInterface.h"
+#include "LogUtils.h"
 
 LogBufferInterface::LogBufferInterface() {
 }
 LogBufferInterface::~LogBufferInterface() {
-}
\ No newline at end of file
+}
+uid_t LogBufferInterface::pidToUid(pid_t pid) {
+    return android::pidToUid(pid);
+}
+pid_t LogBufferInterface::tidToPid(pid_t tid) {
+    return android::tidToPid(tid);
+}