RFR 8143047: Re-examine javax/management/ImplementationVersion/ImplVersionTest.java

[Jaroslav Bachorik]

Please, review the following simple change

Issue : https://bugs.openjdk.java.net/browse/JDK-8143047
Webrev: http://cr.openjdk.java.net/~jbachorik/8143047/webrev.00

The patch removes the special path taken when jmxrmi.jar is present on 
the bootclasspath. There are two reasons for this cleanup:
1. Bootclasspath will not be available (or meaningful) in Jigsaw
2. We haven't been testing with an external jmxrmi.jar for ages - since 
JMX was included into JDK in JDK 5.

The modified test is still passing.

-JB-