For ipa versions prior to 4.5 it is needed to use ipa-client-install script
as a source for functions. But the script contains a global finally clause
in which the generated ccache file gets removed. Threfore the script is
temporarily copied to ipa_client_install.py and the global finally clause
gets removed from the copy. All this is done in a temporary directory, which
gets removed right after the import has been done.