ota_from_target_files: Don't validate data signatures with data wipe

If data is going to be wiped later in the script, there is no reason to
validate signatures. This breaks updates that may be designed to wipe
data and change signatures.

Change-Id: I0b794b43cec2d22996eaa5571688c66582475d55
Ticket: CYNGNOS-1289
1 file changed