BMK-122 Update main.sh, check failures of test singularity and remove images created by singularity

Closes BMK-122

build-executor/main.sh

@@ -19,12 +19,10 @@ function fail(){
 }
 
 function execute_command(){
-  date
-  echo "[execute_command] Executing '$@'"
+  echo "`date` [execute_command] Executing '$@'"
   eval "$@"
   status=$?
-  echo "[execute_command] Return code: ${status}"
-  date
+  echo "`date` [execute_command] Return code: ${status}"
   return ${status}
 }