8067442: Tests using -Xshare:dump does not work with 'make test'

[Erik Helin]

Hi all,

this patch changes the dependency for the target `test` in make/Main.gmk
from exploded-image to jimages. This is needed because PRODUCT_HOME in
`make test` needs to be set to a full JDK image directory, because there
are tests in hotspot/test that uses -Xshare:dump and -Xshare:dump does
not work with an exploded jdk image.

There are currently 9 tests that are failing due to this when running:
$ make test TEST=hotspot_runtime

Webrev:
http://cr.openjdk.java.net/~ehelin/8067442/webrev.00/

Bug:
https://bugs.openjdk.java.net/browse/JDK-8067442

Testing:
- Run `make test TEST=hotspot_runtime` on Linux x86-64 and verified
  that all tests now passes.

Thanks,
Erik