pvcreate: Fix cache state with filters/sig wiping.

pvcreate: Fix cache state with filters/sig wiping.

_pvcreate_check() has two missing requirements:
  After refreshing filters there must be a rescan.
    (Otherwise the persistent filter may remain empty.)
  After wiping a signature, the filters must be refreshed.
    (A device that was previously excluded by the filter due to
     its signature might now need to be included.)

If several devices are added at once, the repeated scanning isn't
strictly needed, but we can address that later as part of the command
processing restructuring (by grouping the devices).

Replace the new pvcreate code added by commit
54685c20fc9dfb155a2e5bc9d8cf5f0aad944305 "filters: fix regression caused
by commit e80884cd080cad7e10be4588e3493b9000649426"
with this change to _pvcreate_check().

The filter refresh problem dates back to commit
acb4b5e4de3c49d36fe756f6fb9997ec179b89c2 "Fix pvcreate device check."