fix regex-typo in lxc-monitor.sgml.in
fix regex-typo in lxc-monitor.sgml.in

To match names beginning with the letters "f" or "b" one can use
the regular expression "[fb].*" or "(f|b).*", but not "[f|b].*",
which would match strings beginning with "f", "|", or "b".

Signed-off-by: Christian von Roques <8bcd0cfb7744b8016edcb992dd9ce34d752a6c01@z12.ch>

caglar10ur/lxc,terceiro/lxc,ss1h2a3tw/lxc,thmo/lxc,thmo/lxc,ss1h2a3tw/lxc,terceiro/lxc,terceiro/lxc,caglar10ur/lxc,thmo/lxc,hallyn/lxc,hallyn/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,hallyn/lxc