lava_rpc_connector.py: Fix typo and use logging for errors

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I86562c290cf1fd9dc3a9b0062a4623d16cb04f2e
diff --git a/tfm_ci_pylib/lava_rpc_connector.py b/tfm_ci_pylib/lava_rpc_connector.py
index 72864a8..b070cfc 100644
--- a/tfm_ci_pylib/lava_rpc_connector.py
+++ b/tfm_ci_pylib/lava_rpc_connector.py
@@ -185,7 +185,7 @@
 
         try:
             if not self.validate_job_yaml(job_definition):
-                print("Served rejected job's syntax")
+                _log.error("Server rejected job's syntax")
                 raise Exception("Invalid job")
             with open(job_definition, "r") as F:
                 job_data = F.read()