MAN: Updating option ipa_server_mode in man sssd-ipa
Changes done for section ipa_server_mode since description of section was bit vague. Text is re-phrased for better understanding.
Resolves: https://pagure.io/SSSD/sssd/issue/3404
Reviewed-by: Fabiano FidĂȘncio <fidencio@redhat.com>