Make an EADDRINUSE on server bind fatal.

This is important because if we try to rebind after a migration and
someone else is in the way, any clients trying to reconnect to us will
instead be connecting to the squatter.

src/serve.c

@@ -232,13 +232,21 @@ void serve_bind( struct server * serve )
 				 * Any of these other than EACCES, 
 				 * EADDRINUSE or EADDRNOTAVAIL signify
 				 * that there's a logic error somewhere.
+				 * 
+				 * EADDRINUSE is fatal: if there's
+				 * something already where we want to be
+				 * listening, we have no guarantees that
+				 * any clients will cope with it.
 				 */
 				case EACCES:
-				case EADDRINUSE:
 				case EADDRNOTAVAIL:
 					debug("retrying");
 					sleep(1);
 					continue;
+				case EADDRINUSE:
+					fatal( "%s port %d in use, giving up.",
+							s_address, 
+							ntohs(serve->bind_to.v4.sin_port));
 				default:
 					fatal( "Giving up" );
 			}

tests/acceptance/fakes/source/successful_transfer.rb

@@ -17,13 +17,5 @@ client.send_mirror()
 
 sleep(1)
 
-squatter.close()
-
-sleep(1)
-
-client2 = FakeSource.new( newaddr, newport.to_i, "Timed out reconnecting" )
-client2.read_hello
-client2.read( 0, 8 )
-client2.close
 
 exit( 0 )

tests/acceptance/flexnbd.rb

@@ -317,8 +317,13 @@ class FlexNBD
       _, status = Process.waitpid2( pid )
 
       if @kill
-        fail "flexnbd quit with a bad status: #{status.exitstatus}" unless
+        if status.signaled?
+          fail "flexnbd quit with a bad signal: #{status.inspect}" unless
+            @kill.include? status.termsig
+        else
+          fail "flexnbd quit with a bad status: #{status.inspect}" unless
             @kill.include? status.exitstatus
+        end
       else
         $stderr.puts "flexnbd #{self.pid} quit"
         fail "flexnbd #{self.pid} quit early with status #{status.to_i}"

tests/acceptance/test_dest_error_handling.rb

@@ -80,7 +80,8 @@ class TestDestErrorHandling  < Test::Unit::TestCase
   end
 
 
-  def test_cant_rebind_retries
+  def test_cant_rebind_dies
+    @env.nbd1.can_die(6)
     run_fake( "source/successful_transfer" )
   end