used setHeader instead of addHeader for decorator

Author: Bilal Al

client/src/main/java/io/split/client/RequestDecorator.java

@@ -44,7 +44,7 @@ public HttpUriRequestBase decorateHeaders(HttpUriRequestBase request) {
             Map<String, String> headers = _headerDecorator.getHeaderOverrides();
             for (Map.Entry entry : headers.entrySet()) {
                 if (isHeaderAllowed(entry.getKey().toString())) {
-                    request.addHeader(entry.getKey().toString(), entry.getValue());
+                    request.setHeader(entry.getKey().toString(), entry.getValue());
                 }
             }
         } catch (Exception e) {

client/src/test/java/io/split/client/RequestDecoratorTest.java

@@ -39,6 +39,7 @@ public Map<String, String> getHeaderOverrides() {
         MyCustomHeaders myHeaders = new MyCustomHeaders();
         RequestDecorator decorator = new RequestDecorator(myHeaders);
         HttpGet request = new HttpGet("http://anyhost");
+        request.addHeader("first", "myfirstheader");
         request  = (HttpGet) decorator.decorateHeaders(request);
         Assert.assertEquals(3, request.getHeaders().length);
         Assert.assertEquals("1", request.getHeader("first").getValue());