package/fail2ban: The (host-python3) 2to3 utility needs to be present

During _POST_PATCH_HOOKS _DEPENDANCIES aren't guaranteed to be built,
however during _PRE_CONFIGURE_HOOKS they should be built.

Should fix:
http://autobuild.buildroot.net/results/dd8e225e2a49cfa6735bed11459007003a37c137/
http://autobuild.buildroot.net/results/e688c3652bd474ac682984e2e5947701942f0f57/



Cc: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Pascal de Bruijn <p.debruijn@unilogic.nl>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>