core: Remove the Helper class

org.ovirt.engine.core.utils.Helper had only one method, ToList, which
was, in fact, just creating a new ArrayList around a given iterable.

This patch removes this useless class, and just calls ArrayList's
constructor instead.

Change-Id: I2563766d08aeece478ac7659103f26f19b90deb3
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Remove StringCompatTest

StringCompatTest did not in fact test StringCompat (which was already
removed), but StringHelper's join method.

This method is already thoroughly tested in StringHelperTest, so this
test is redundant and can be removed.

Change-Id: I9fc6ec3759f661e4da54957a2140a4d975cf9546
Signed-off-by: Allon Mureinik <amureini@redhat.com>