fix(outputs.Wavefront): If no "host" tag is provided, do not add "telegraf.host" tag (#11078)

Co-authored-by: ffaroo1 <svc-registry-github@intuit.com>

plugins/outputs/wavefront/wavefront.go

@@ -190,7 +190,10 @@ func (w *Wavefront) buildTags(mTags map[string]string) (string, map[string]strin
 			for k, v := range mTags {
 				if k == s {
 					source = v
-					mTags["telegraf_host"] = mTags["host"]
+					if mTags["host"] != "" {
+						mTags["telegraf_host"] = mTags["host"]
+					}
+
 					sourceTagFound = true
 					delete(mTags, k)
 					break

plugins/outputs/wavefront/wavefront_test.go

@@ -243,6 +243,11 @@ func TestBuildTagsWithSource(t *testing.T) {
 			"r-@l\"Ho/st",
 			map[string]string{"something": "abc"},
 		},
+		{
+			map[string]string{"hostagent": "realHost", "env": "qa", "tag": "val"},
+			"realHost",
+			map[string]string{"env": "qa", "tag": "val"},
+		},
 	}
 
 	for _, tt := range tagtests {