finagle-http2: modify H2ServerFilter to no longer swallow exceptions

Problem/Solution

The `H2ServerFilter` currently swallows any exceptions that get
fired down the pipeline. There is nothing we currently know of
that should explicitly need to be caught here and blindly
swallowing exceptions could mask other issues. Let's remove
it.

JIRA Issues: CSL-8654

Differential Revision: https://phabricator.twitter.biz/D369185

CHANGELOG.rst

@@ -7,6 +7,12 @@ Note that ``PHAB_ID=#`` and ``RB_ID=#`` correspond to associated messages in com
 Unreleased
 ----------
 
+Runtime Behavior Changes
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+* finagle-http2: H2ServerFilter will no longer swallow exceptions that fire via
+  `exceptionCaught` in the Netty pipeline. `PHAB_ID=D369185`
+
 19.9.0
 ------
 

finagle-http2/src/main/scala/com/twitter/finagle/http2/transport/H2ServerFilter.scala

@@ -49,12 +49,6 @@ private[http2] final class H2ServerFilter(timer: Timer) extends ChannelDuplexHan
       super.channelRead(ctx, msg)
   }
 
-  override def exceptionCaught(ctx: ChannelHandlerContext, cause: Throwable): Unit = {
-    // Swallowed so as to not bork the parent pipeline. This includes
-    // GOAWAY messages.
-    ()
-  }
-
   override def close(ctx: ChannelHandlerContext, promise: ChannelPromise): Unit = {
     val connectionHandler = ctx.pipeline.get(classOf[Http2ConnectionHandler])