JDKs (e.g. 11 and 12)

From java 10 onwards package-list has been replaced by element-list file
and this needs to be checked during verification of javadoc. This change
set check for element-list file if package-list file is not present and
validates the api location.

Change-Id: Iede1e5f98924d7ef528f612ff4523fec44f504bc
Signed-off-by: Kalyan Prasad Tatavarthi <kalyan_prasad@in.ibm.com>