minor fix for usbfadm
Initial check for current working directory has been broken (Syntax error of expr command occurred at the root directory). Fixed it.
Note: patch-012 was skipped because the sysupgrade utility is considered not to work correctly on FuguIta.
FuguIta-6.5-arm64-201908082
On arm64, when performing newdrive command of usbfadm, rsync has been failed with I/O error.
Fixed this problem by changing mount option of destination device from async to softdep.