Disable H3 tests by default with a system property to explicitly enable them

[lorban]

As it says on the tin.

[olamy]

we might need something to enable it via command line
in pom of test-http-client-transport, something such:

  <properties>
    <bundle-symbolic-name>${project.groupId}.client.http</bundle-symbolic-name>
    <h3.test.enabled>false</h3.test.enabled>
  </properties>
...
  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-surefire-plugin</artifactId>
          <configuration>
            <systemPropertyVariables>
              <org.eclipse.jetty.http.client.TransportProvider.H3.enable>${h3.test.enabled}</org.eclipse.jetty.http.client.TransportProvider.H3.enable>
            </systemPropertyVariables>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
....

So we can enable this in CI if needed with adding: -Dh3.test.enabled=true
let me know and I can add it (but my tomorrow)

[lorban]

@olamy thanks, added it myself.