mon/OSDMonitor: fix improper input/testing range of crush somke testing

mon/OSDMonitor: fix improper input/testing range of crush somke testing

CrushTester::test() will reset testing range to [0, 1023] whenever
min_x or max_x is negative and the constructor of CrushTester will
always default min_x and max_x to -1.

Thus to set the test range correctly, you have to specify both min_x and max_x.
Local test shows this patch shall decrease the time consumed by the crush
smoke testing to approximate 1/20 of those without this.

For exmaple:
crush somke test duration: 0.668354 seconds ->
crush somke test duration: 0.012592 seconds

Signed-off-by: xie xingguo <xie.xingguo@zte.com.cn>