Enhance get_size() function
Enhance get_size() function

So that it can handle units like 'KiB', 'MiB', 'GiB', 'TiB' etc.
It is also takes spaces and floating numbers in consideration.

Signed-off-by: Qun Li <1ea81f54854048d0a4d4fd61caceabb2a843281c@zstack.io>

zstackio/zstack-utility,zstackorg/zstack-utility,zstackorg/zstack-utility,zstackio/zstack-utility,zstackio/zstack-utility,zstackorg/zstack-utility