Fix travis to enforce older DateTime module.
Fix travis to enforce older DateTime module.

xhoy/otrs,MBRG/otrs,mburggraf/otrs,s7design/otrs,rudy500/otrs,rudy500/otrs,xhoy/otrs,s7design/otrs,mburggraf/otrs,xhoy/otrs,MBRG/otrs,rudy500/otrs,mburggraf/otrs,xhoy/otrs,MBRG/otrs,rudy500/otrs,MBRG/otrs,mburggraf/otrs,xhoy/otrs,MBRG/otrs,mburggraf/otrs,rudy500/otrs,s7design/otrs,s7design/otrs,s7design/otrs