RFR JDK-8211051: jdeps usage of --dot-output doesn't provide valid output for modular jar

[Mandy Chung]

This is a small fix to jdeps --dot-output option that should
name the dot file with the filename of the modular JAR rather
than its module name.

http://cr.openjdk.java.net/~mchung/jdk12/webrevs/8211051/webrev.00/

Thanks
Mandy