liblog: reset pid and uid cache after a vfork()

Bionic getuid() and getpid() calls cache to reduce the need to
perform a syscall, and also reset their own cache after a vfork().
No more need for liblog to be performing this flawed cache operation.

Bug: 30085794
Change-Id: I70feed8bff0ddd919c2885a348ba67b14ddc0e0d
diff --git a/liblog/pmsg_writer.c b/liblog/pmsg_writer.c
index 2ba31fa..944feba 100644
--- a/liblog/pmsg_writer.c
+++ b/liblog/pmsg_writer.c
@@ -142,7 +142,7 @@
     pmsgHeader.magic = LOGGER_MAGIC;
     pmsgHeader.len = sizeof(pmsgHeader) + sizeof(header);
     pmsgHeader.uid = __android_log_uid();
-    pmsgHeader.pid = __android_log_pid();
+    pmsgHeader.pid = getpid();
 
     header.id = logId;
     header.tid = gettid();