Fixed improper size displaying in 'df' utility

'df' command used to display filesystem usage statistics as integer
values, in most cases rounding the actual value down. Because of
that 'df' tended to display faulty size values.
This fix to 'df' utility calculates the fractional part of the size,
then it rounds it when needed to the nearest one-digit integer value
and displays after decimal dot.

(cherry picked from commit 1f90dcd0c022182220c37b300690cf73674d03b8)

Change-Id: If215e1c525ffc74c3dd9ad1b8674f418c729d602