`org.apache.karaf.specs.timeout` should be removed

• The following options should be removed from etc/system.properties. These are to better support JDK9+ (1) . However, we only support JDK8 for FUSE 7.0, 7.1, 7.2. So these may cause confusion (though harmless for functionality).
  ~~~
  org.apache.karaf.specs.debug = false
  org.apache.karaf.specs.timeout = 0
  ~~~

• The above options are originally from Apache Servicemix, which is used for enabling SPI mechanism in OSGi.
  ~~~
  org.apache.servicemix.specs.debug = false
  org.apache.servicemix.specs.timeout = 0
  ~~~

• As of now, the both of the options (org.apache.servicemix.xxx and org.apache.karaf.specs.xxx) are included in etc/system.properties.

(1) Provide support for xml parsers deployed as bundle on Java 9
    https://issues.apache.org/jira/browse/KARAF-5680