* crates.io keeps yanked packages with the "yanked" attribute.
For example, log-0.4.9 and log-0.4.10 were yanked so
"get_rust_pkg log" should skip them.
* Compare version numbers before the publish id number.
For example, lazy_static-1.1.1 was published after lazy_static-1.4.0,
but "get_rust_pkg lazy_static" should fetch 1.4.0.
Test: get_rust_pkg.py -v log # get log.0.4.8
Test: get_rust_pkg.py -v log-0.4.10 # get log.0.4.10
Test: get_rust_pkg.py -v lazy_static # get lazy_static-1.4.0
Change-Id: Id005a91b75c0885285a76136bd6de19d0dafa5c1
7c6362a96b