Minimize differences in ifstart() function between netstart and

Minimize differences in ifstart() function between netstart and
install.sub which makes it easier to spot changes in the future.

- comments and formatting
- quotes on assignments are not needed (netstart)
- remove stray space in test (netstart)
- use $file variable with while-loop (netstart)
- although valid, instead of i use $i in arithmetic test (install.sub)

OK krw@, tb@
Looks good deraadt@