network/net-lib.sh: fix ibft interface configuration

also skip ibft$num names, which have been already given

https://bugzilla.redhat.com/show_bug.cgi?id=989944
iscsi/module-setup.sh: install some modules regardless of hostonly
multipath: need_shutdown if multipath devices exist

https://bugzilla.redhat.com/show_bug.cgi?id=994913
omit drivers fix

Because omit_drivers list use underline always, so when maching with it
the _mod need to be converted as well or sometimes omit-drivers will fail
silently.

Fix this by replace '-' with '_' in instmods function.

Signed-off-by: Dave Young <dyoung@redhat.com>