fix-issue-434 To add proxy related settings to splunk connector

Signed-off-by: Wang, Shu <shu.wang@fmr.com>

Author: wangshu3000

src/main/java/com/splunk/kafka/connect/SplunkSinkConnectorConfig.java

@@ -437,7 +437,7 @@ public String toString() {
                 + "headerCustom:" + headerCustom + ", "
                 + "httpKeepAlive:" + httpKeepAlive + ", "
                 + "httpProxyHost:" + httpProxyHost + ", "
-                + "httpProxyPort:" + httpProxyPort
+                + "httpProxyPort:" + httpProxyPort + ", "
                 + "validateCertificates:" + validateCertificates + ", "
                 + "trustStorePath:" + trustStorePath + ", "
                 + "trustStoreType:" + trustStoreType + ", "