arcstat: flush stdout / outfile after each line

Otherwise, if arcstat gets interrupted before the desired number of
iterations is reached, the output file will be empty (both if set via
'-o' or via shell redirection).

Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Giuseppe Di Natale <[email protected]>
Signed-off-by: Fabian Grünbichler <[email protected]>
Closes #6775 

0 files changed, 0 insertions, 0 deletions