[FAB-13189] set content-type for logspec response

Change-Id: I4538e9c2f2f0f16e0a0362aa71df8496fe4228fd
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>

common/flogging/httpadmin/spec.go

@@ -75,6 +75,7 @@ func (h *SpecHandler) sendResponse(resp http.ResponseWriter, code int, payload i
 
 	resp.WriteHeader(code)
 
+	resp.Header().Set("Content-Type", "application/json")
 	if err := encoder.Encode(payload); err != nil {
 		h.Logger.Errorw("failed to encode payload", "error", err)
 	}

common/flogging/httpadmin/spec_test.go

@@ -41,6 +41,7 @@ var _ = Describe("SpecHandler", func() {
 		Expect(fakeLogging.SpecCallCount()).To(Equal(1))
 		Expect(resp.Code).To(Equal(http.StatusOK))
 		Expect(resp.Body).To(MatchJSON(`{"spec": "the-returned-specification"}`))
+		Expect(resp.Header().Get("Content-Type")).To(Equal("application/json"))
 	})
 
 	It("sets the current logging spec", func() {