[LIBCLOUD-551] Fix Google DNS to use valid record split character

@franckcuny - mind looking this over?

I ran into this because one of my testing domains was foo-bar.com.  When trying to look up a record with get_record(), I formed "foo-bar.com-A" and the get_records()'s split() call failed on unpacking the string.

Looking over other providers, it seems they've all settled on using ':'.  I also swapped the record type / name ordering for unpacking to make it more compatible with the other providers.