fix logfile counting in months != january

fix logfile counting in months != january

the changes introduced in 1cdbebe57b2ddc255db240d7dbaf2165c482986d

changed the date handling to have current_month and current_year
represent the month and year at time of invocation.
This change was not carried over to the logfile collecting, which set
the current month to january.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Tested-by: Aaron Lauterer <a.lauterer@proxmox.com>
Reviewed-by: Mira Limbeck <m.limbeck@proxmox.com>