qa/suites: disable mon crush smoke test with valgrind

qa/suites: disable mon crush smoke test with valgrind

Valgrind runs itself on forked children, and does its cleanup when they
complete, and this is slow... slow enough that it frequently makes the
test time out.

Valgrind let's you ignore child *processes* that you exec, but I can't
find a way to skip forked children in the same address space.

Work around this by skip this validation when running under valgrind.

Fixes: http://tracker.ceph.com/issues/20602
Signed-off-by: Sage Weil <sage@redhat.com>