Issue
=====
The original issue was that the size of a fil_per_table tablespace was calculated
incorrectly during truncate in the presence of an fts index. This incorrect calculation
was fixed as part of BUG#25053705 along with a testcase to reproduce the bug. The
assert that was added as part of it to reproduce the bug was wrong and resulted in
this bug.

Fix
===
Although the assert was removed earlier in a seperate commit as it was blocking the
ntest, this patch replaces the other parts of the code that were added to reproduce
the bug and replaces it with code that tries to reproduce the bug in a different way.

The new code basically tries to tweak conditions so as to simulate the random read
where a page that doesn't exist is tried to be read.

RB: 15890
Reviewed-by: Jimmy Yang <Jimmy.Yang@oracle.com>
Reviewed-by: Satya Bodapati <satya.bodapati@oracle.com>