gluster:Datatype change for bytesRead & bytesWritten from int to long.

This patch changes the datatype of bytesRead and bytesWritten from int
to long to avoid the data overflow that may occur.

Change-Id: I5dd8f372059a4d0616bef34325e23d88a959bcba
Bug-url: https://bugzilla.redhat.com/show_bug.cgi?id=1015013
Signed-off-by: ndarshan <dnarayan@redhat.com>