* output: define unlimited/none retry configurtion constant
* engine: support no retry configuration(#3190)
* sosreport: use FLB_OUT_RETRY_UNLIMITED define
* output: set default value when invalid retry_limit is set
* output: support no_retries/no_limits as retry_limits value

Signed-off-by: Takahiro Yamashita <nokute78@gmail.com>