set static pass key for nrf51822 in example code--hrs with dfu ，nrf51822 reboot

[RiverYWang]

we add static pass key in example code hrs with dfu，but when connecting with phone，input passkey on phone，the nrf51822 will rebootdevice_manager_cnfg.h main.c

[Susheel Nuguru]

sorry for late reply, i was sick, which sdk did you try this on? I shall try it on my desk and see why it happens, I just need to know sdk version.