tee: minor cleanup

[kevans]

Summary

Pull the open flags out of the loop into a local var. They won't be
changing, so this is marginally more readable.

Adds some extra brackets around the loop in preparation for a future
change that may try to fallback to opening the path as a socket if we
get an EOPNOTSUPP.

No functional change.

[kevans]

omode -> oflags

[emaste]

I think the added braces are an improvement even absent the subsequent change.

[des]

usr.bin/tee/tee.c

62

I would merge the two int lines and the two char * lines.

100–102

I'd prefer braces around this line.

[kevans]

usr.bin/tee/tee.c

62

Also re-sorted