We need to check if file system size is equal to provider's size, because
sysinstall(8) still bogusly puts the first partition at offset 0 instead of 16,
so glabel/ufs will find file system on a slice instead of partition.
Before sysinstall is fixed, we must keep this code, which means that we
wont't be able to detect UFS file systems created with 'newfs -s ...'.
PS. bsdlabel(8) creates partitions properly.
Approved by: re (hrs)
c44fa9d800