v23/rpc: Switch ServerCall.Server to return an XServer.

MultiPart: 1/2
Change-Id: If1ae35276eade7a6685d50a6e5b841d8c9d180b8
diff --git a/runtime/internal/rpc/server.go b/runtime/internal/rpc/server.go
index 9f97089..52be186 100644
--- a/runtime/internal/rpc/server.go
+++ b/runtime/internal/rpc/server.go
@@ -1338,7 +1338,7 @@
 	//nologcall
 	return fs.discharges
 }
-func (fs *flowServer) Server() rpc.Server {
+func (fs *flowServer) Server() rpc.XServer {
 	//nologcall
 	return fs.server
 }
diff --git a/runtime/internal/rpc/xserver.go b/runtime/internal/rpc/xserver.go
index 3907975..6b98b09 100644
--- a/runtime/internal/rpc/xserver.go
+++ b/runtime/internal/rpc/xserver.go
@@ -769,7 +769,7 @@
 	//nologcall
 	return fs.flow.RemoteDischarges()
 }
-func (fs *xflowServer) Server() rpc.Server {
+func (fs *xflowServer) Server() rpc.XServer {
 	//nologcall
 	return nil // TODO(toddw): Change return to rpc.XServer
 }
diff --git a/services/mounttable/mounttablelib/mounttable_test.go b/services/mounttable/mounttablelib/mounttable_test.go
index ae52282..3cca456 100644
--- a/services/mounttable/mounttablelib/mounttable_test.go
+++ b/services/mounttable/mounttablelib/mounttable_test.go
@@ -450,7 +450,7 @@
 func (fakeServerCall) LocalEndpoint() naming.Endpoint       { return nil }
 func (fakeServerCall) RemoteEndpoint() naming.Endpoint      { return nil }
 func (fakeServerCall) GrantedBlessings() security.Blessings { return security.Blessings{} }
-func (fakeServerCall) Server() rpc.Server                   { return nil }
+func (fakeServerCall) Server() rpc.XServer                  { return nil }
 func (c *fakeServerCall) SendStream() interface {
 	Send(naming.GlobReply) error
 } {
diff --git a/services/syncbase/vsync/responder_test.go b/services/syncbase/vsync/responder_test.go
index dbd0fea..135830c 100644
--- a/services/syncbase/vsync/responder_test.go
+++ b/services/syncbase/vsync/responder_test.go
@@ -487,7 +487,7 @@
 	return security.Blessings{}
 }
 
-func (d *dummyResponder) Server() rpc.Server {
+func (d *dummyResponder) Server() rpc.XServer {
 	return nil
 }
 
diff --git a/services/wspr/internal/app/app.go b/services/wspr/internal/app/app.go
index 6edb6c0..0b22d86 100644
--- a/services/wspr/internal/app/app.go
+++ b/services/wspr/internal/app/app.go
@@ -429,7 +429,7 @@
 }
 func (l *localCall) Recv(interface{}) error                          { return nil }
 func (l *localCall) GrantedBlessings() security.Blessings            { return security.Blessings{} }
-func (l *localCall) Server() rpc.Server                              { return nil }
+func (l *localCall) Server() rpc.XServer                             { return nil }
 func (l *localCall) Timestamp() (t time.Time)                        { return }
 func (l *localCall) Method() string                                  { return l.vrpc.Method }
 func (l *localCall) MethodTags() []*vdl.Value                        { return l.tags }