s4:torture Cut the RPC-SAMR-LARGE-DC test down to size

s4:torture Cut the RPC-SAMR-LARGE-DC test down to size

This removes the validation of the estimated number of accounts,
because MS-SAMR 3.1.5.5.1.1 makes clear the number returned cannot be
relied apon.

I've also converted a bit more of the test to use torture_assert(),
and where that is impractical, to print error messages when things
fail.

Andrew Bartlett