Cast Integer Argument To Unsigned Char

The member reg in the peercnt structure is an unsigned char and peercnt_modify()
is expecting an unsigned char argument which gets assigned to peercnt->reg.

This patch fixes that by casting the integer argument being passed to
peercnt_modify to unsigned char.
........

Merged revisions 400314 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@400315 f38db490-d61c-443f-a65b-d21fe96a405b