Lower Chasing_The_Leader rate threshold

With the rate threshold set at 50, this
test fails frequently. Not sure why that
threshold was picked but lowered it to 10.
Looking at past runs, the actual rate
fluctuates anywhere between 20-80, which is
indicative of the unpredictablity of load in
the CS environment as the related
production code is mostly network I/O bound.

Change-Id: Id579c9553e0e48c85c039de5fddb0d1e56a5f2e6
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>