Make jetty-10 amenable to testing with SNAPSHOT jsp jars

[janbartel]

jetty-10

Use the same pom.xml code as in jetty-11 to convert a version that may include SNAPSHOT into an osgi-acceptable form:

      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>build-helper-maven-plugin</artifactId>
        <executions>
          <execution>
              <id>set-jsp-api-version</id>
              <phase>validate</phase>
              <goals>
                  <goal>parse-version</goal>
              </goals>
              <configuration>
                  <versionString>${jsp.impl.version}</versionString>
                  <propertyPrefix>jspImpl</propertyPrefix>
              </configuration>
          </execution>
        </executions>
      </plugin>