vts: split kselftests and ltp

Split the location of ltp and kselftest files so that they are not
uploaded together if running individually.  Should improve the
performance of kselftest.

Bug: 190800715
Test: atest vts_ltp_test_x86_64
Test: atest vts_linux_kselftest_x86_64
Signed-off-by: Edward Liaw <edliaw@google.com>
Change-Id: I121e6d5bab8edd185c8d73ad7849dff9e8b5f118