BUG: disk usage unit is wrong

[wwng2333]

agent version: 0.7.3
os: alpine on LXC
I used about 900MB disk, but beszel shows that only used 0.9MB.

mofvd44x:~# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/loop44               1.9G    917.4M    910.1M  50% /
none                    492.0K      4.0K    488.0K   1% /dev
udev                     62.8G         0     62.8G   0% /dev/net/tun
udev                     62.8G         0     62.8G   0% /dev/full
udev                     62.8G         0     62.8G   0% /dev/null
udev                     62.8G         0     62.8G   0% /dev/random
udev                     62.8G         0     62.8G   0% /dev/tty
udev                     62.8G         0     62.8G   0% /dev/urandom
udev                     62.8G         0     62.8G   0% /dev/zero
none                    492.0K      4.0K    488.0K   1% /proc/sys/kernel/random/boot_id
tmpfs                    25.1G    160.0K     25.1G   0% /run
shm                      62.9G         0     62.9G   0% /dev/shm

[henrygd]

Same issue as #261. Fix has been added for the next release.