fix dump stakerd.conf by permission denied

[fyInALT]

Fix

 ./build/stakercli admin dump-config 

Failed by mkdir mode:

[btc-staker] open /home/fy/.stakerd/stakerd.conf: permission denied

it caused by use error mod:

if err := os.MkdirAll(dir, os.ModeDir); err != nil {

this will make path mode be:

d---------  2 fy   fy   4.0K Oct 15 09:33 .stakerd

Now we should use 0700, as dir 's mode.