Fix always fetch Zabbix version before issuing new requests (#2133)

Previously we were only fetching the version when the version was `0`.
This generally worked, but posed some problems when customers were
updating their Zabbix version, specifically when upgrading from a
version < `7.2.x` to `7.2.x` or above.

Before `7.2.x`, an `auth` parameter was still supported when issuing a
zabbix request, this was deprecated in `6.4.x` and later removed in
`7.2.x`. When a user was on a version < `7.2.x` all the outgoing
requests would add this `auth` parameter. When upgrading to `7.2.x` this
was a problem, because the version was not `0`, hence, not requiring
getting the version again, but also because we were still building the
request considering an older version and adding the `auth` parameter,
when this was no longer supported.

This PR removes the check for `version == 0`, though this now means that
every request that goes out will check the version before hand, I think
this will give us a more accurate representation of the version that
needs to be used.

fixes
https://github.com/orgs/grafana/projects/457/views/40?pane=issue&itemId=3683181283&issue=grafana%7Coss-big-tent-squad%7C135

pkg/zabbix/zabbix_test.go

@@ -83,15 +83,23 @@ func TestNonCachedQuery(t *testing.T) {
 }
 
 func TestItemTagCache(t *testing.T) {
-	zabbixClient, _ := MockZabbixClient(
-		BasicDatasourceInfo,
-		`{"result":[{"itemid":"1","name":"test1"}]}`,
-		200,
-	)
+	callCount := 0
+	zabbixClient := NewZabbixClientWithHandler(t, func(payload ApiRequestPayload) string {
+		switch payload.Method {
+		case "apiinfo.version":
+			return `{"result":"6.4.0"}`
+		case "item.get":
+			callCount++
+			if callCount == 1 {
+				return `{"result":[{"itemid":"1","name":"test1"}]}`
+			}
+			return `{"result":[{"itemid":"2","name":"test2"}]}`
+		default:
+			return `{"result":null}`
+		}
+	})
 	// tag filtering is on >= 54 version
-	zabbixClient.version = 64
 	zabbixClient.settings.AuthType = settings.AuthTypeToken
-	zabbixClient.api.SetAuth("test")
 	items, err := zabbixClient.GetAllItems(
 		context.Background(),
 		nil,