Fix $&if to run "elses" like "thens", not "tests"

[jpco]

Found while looking at #73; if "turns off" the exit-on-false behavior when running each test, but the current behavior has it also do so while running the else command, which seems pretty clearly wrong.

if {false} {
  command which will not run
} {
  commands that might
  be risky
  don''''t you want
  some -e protection here?
}

The fact that this has never been reported before is, along with the fact that the bodies of while loops run with eval_exitonfalse toggled off, is pretty compelling evidence to me that nobody ever uses -e...