UNOMI-370: fix device category resolution by using setter correctly. (#192)

diff --git a/plugins/request/src/main/java/org/apache/unomi/plugins/request/useragent/UserAgent.java b/plugins/request/src/main/java/org/apache/unomi/plugins/request/useragent/UserAgent.java
index 04b2fd3..6980b3a 100644
--- a/plugins/request/src/main/java/org/apache/unomi/plugins/request/useragent/UserAgent.java
+++ b/plugins/request/src/main/java/org/apache/unomi/plugins/request/useragent/UserAgent.java
@@ -83,7 +83,7 @@
     }
 
     public void setDeviceName(String deviceName) {
-        this.deviceCategory = deviceName;
+        this.deviceName = deviceName;
     }
 
     public String getUserAgentNameAndVersion() {