tests: tail-2/assert: reduce risk of race condition

* tests/tail2/assert: This reverts commit be853120, 25-08-2009,
"tests: tail-2/assert: avoid risk of race condition"
kill -0 doesn't send a signal and so will only confirm that the
background process was forked, which we know already because
we have its pid.

tests/tail-2/assert

@@ -42,13 +42,9 @@ tail_pid=$!
 
 echo sleeping for 7 seconds...
 
-# Wait for the backgrounded `tail' to start before removing foo.
+# Give the backgrounded `tail' a chance to start before removing foo.
 # Otherwise, without --retry, tail wouldn't try to open `foo' again.
-while :; do
-  env kill -0 $tail_pid && break
-  echo sleep .1
-  sleep .1
-done
+sleep 1
 
 rm -f foo
 sleep 6