Upgrade maven-surefire-plugin to 2.22.1

Move the version to a property so it only needs to be changed in
one place next time.

Change-Id: Id21773be4829fa1787ef19eb3a76a44bcd3f8377

pom.xml

diff --git a/pom.xml b/pom.xml
index 90d1aa1..0c25b53 100644
--- a/pom.xml
+++ b/pom.xml
@@ -263,6 +263,7 @@
 
   <properties>
     <java.version>1.8</java.version>
+    <maven-surefire-version>2.22.1</maven-surefire-version>
   </properties>
 
   <profiles>
@@ -301,7 +302,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-surefire-plugin</artifactId>
-          <version>2.20</version>
+          <version>${maven-surefire-version}</version>
           <configuration>
             <additionalClasspathElements>
               <additionalClasspathElement>${maxdb.driver.jar}</additionalClasspathElement>
@@ -318,7 +319,7 @@
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-surefire-plugin</artifactId>
-            <version>2.20</version>
+            <version>${maven-surefire-version}</version>
             <configuration>
               <additionalClasspathElements>
                 <additionalClasspathElement>${hana.driver.jar}</additionalClasspathElement>