Refactor: based: Simplify based_callbacks.c:prepare_input()

The input variable gets assigned the child of F_CIB_CALLDATA, not the
F_CIB_CALLDATA element itself. In Pacemaker 1.1.11 and currently,
F_CIB_CALLDATA's child is never F_CRM_DATA nor another F_CIB_CALLDATA
element. So the pcmk__str_any_of() condition is always false.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>