tools/lib/lockdep: Hide liblockdep output from test results

tools/lib/lockdep: Hide liblockdep output from test results

This would prevent the liblockdep error messages from getting
mixed in with the test result output.

Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: a.p.zijlstra@chello.nl
Cc: ben@decadent.org.uk
Link: http://lkml.kernel.org/r/20170525130005.5947-22-alexander.levin@verizon.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>