Zabbix

.......... [DEV-2645] fixed processing of date string with month related operations for SLA report widget autotest

* commit '63a3fc933d8f627d2bd39ecc38e7fd1007d29941':
  .......... [DEV-2645] moved detection of months in date string to normalizeDate method and fixed issue with leap year
  .......... [DEV-2645] moved date string conversion to desired format so that widgets with all types of reporting period would use it
  .......... [DEV-2645] created a function to convert string to required date format without direct usage of strtotime