[Xymon] Fix - trivial comment change in code

Hello,

Xymon 4.3.7 xymonnet.c has the following line (line 491):

 * - '|' denotes reverse test, i.e. service should be DOWN.

Surely the '|' should be a '!' character.

John.

-- John Horne Tel: +44 (0)1752 587287 Plymouth University, UK Fax: +44 (0)1752 587001