Use ro.logd.kernel for kernel logcat

Prevent a possible DOS of the kernel logs because the runtime result
could differ from the boottime result.

Test: adb bugreport, then examine kernel log
Change-Id: I140fd465f2e691c751d92af50dbdf95e23c121d8
diff --git a/logd/main.cpp b/logd/main.cpp
index c8183f0..4af0d21 100644
--- a/logd/main.cpp
+++ b/logd/main.cpp
@@ -438,8 +438,8 @@
 
     int fdPmesg = -1;
     bool klogd = __android_logger_property_get_bool(
-        "logd.kernel", BOOL_DEFAULT_TRUE | BOOL_DEFAULT_FLAG_PERSIST |
-                           BOOL_DEFAULT_FLAG_ENG | BOOL_DEFAULT_FLAG_SVELTE);
+        "ro.logd.kernel",
+        BOOL_DEFAULT_TRUE | BOOL_DEFAULT_FLAG_ENG | BOOL_DEFAULT_FLAG_SVELTE);
     if (klogd) {
         static const char proc_kmsg[] = "/proc/kmsg";
         fdPmesg = android_get_control_file(proc_kmsg);