logd: don't use SIGHUP to reinitialize

It doesn't look like there are any users, since there is a much better
mechanism, `logd --reinit` that exists for this behavior.  The
settings app and init.rc use that mechanism and they are the two major
clients that force logd to reinitialize.

This saves us from creating a thread and marginally cleans up
main.cpp.

Test: log reinitialization works
Change-Id: Icdb56b6f59adbba82812231a4f3a6ffd1a7955fc
diff --git a/logd/LogBuffer.cpp b/logd/LogBuffer.cpp
index 443fd98..7e1bb0a 100644
--- a/logd/LogBuffer.cpp
+++ b/logd/LogBuffer.cpp
@@ -92,11 +92,7 @@
         unlock();
     }
 
-    // We may have been triggered by a SIGHUP. Release any sleeping reader
-    // threads to dump their current content.
-    //
-    // NB: this is _not_ performed in the context of a SIGHUP, it is
-    // performed during startup, and in context of reinit administrative thread
+    // Release any sleeping reader threads to dump their current content.
     LogTimeEntry::wrlock();
 
     LastLogTimes::iterator times = mTimes.begin();