binderSafeInterfaceTest: over maxFds, not double

This test is timing out, so test only 100 more calls
than maxFds instead of double that number. This still
will check against leaks, but limit the total time
that this testcase takes to run.

Fixes: 283165591
Test: binderSafeInterfaceTest

Change-Id: Ib022d29905997f65bfe85b83a1ff01848d16bd3b