GH-3243: sync computeIfAbsent in StoredProcExec

Fixes #3243

It turns out that `ConcurrentModificationException` is thrown from the
`HashMap.computeIfAbsent(HashMap.java:1134)` since Java 9 when the map is
modified concurrently independently from the key we try to modify

* Check for the value presence before computing
* `synchronized(this.jdbcCallOperationsMap)` around `computeIfAbsent()`
when `get() == null`

**Cherry-pick to 5.2.x**

Author: artembilan

spring-integration-jdbc/src/main/java/org/springframework/integration/jdbc/StoredProcExecutor.java

@@ -62,6 +62,8 @@ public class StoredProcExecutor implements BeanFactoryAware, InitializingBean {
 
 	private final DataSource dataSource;
 
+	private final Object jdbcCallOperationsMapMonitor = new Object();
+
 	private Map<String, RowMapper<?>> returningResultSetRowMappers = new HashMap<>(0);
 
 	private EvaluationContext evaluationContext;
@@ -296,7 +298,14 @@ private Map<String, Object> executeStoredProcedureInternal(Object input, String
 	}
 
 	private SimpleJdbcCallOperations obtainSimpleJdbcCall(String storedProcedureName) {
-		return this.jdbcCallOperationsMap.computeIfAbsent(storedProcedureName, this::createSimpleJdbcCall);
+		SimpleJdbcCallOperations operations = this.jdbcCallOperationsMap.get(storedProcedureName);
+		if (operations == null) {
+			synchronized (this.jdbcCallOperationsMapMonitor) {
+				operations =
+						this.jdbcCallOperationsMap.computeIfAbsent(storedProcedureName, this::createSimpleJdbcCall);
+			}
+		}
+		return operations;
 	}
 
 	//~~~~~Setters for Properties~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~