statistics: bug fix - change of month 

git-svn-id: svn://svn.code.sf.net/p/fhem/code/trunk@6795 2b470e98-0d58-463d-a4d8-8e2adae1ed80
98_PID20 : fix in sub PID20_Set : wrong parameter, when calling PID20_Calc

git-svn-id: svn://svn.code.sf.net/p/fhem/code/trunk@6796 2b470e98-0d58-463d-a4d8-8e2adae1ed80