ota: Validate any installed data's signature against our own

Try to prevent incompatible-signature system quirkiness

Change-Id: I73402d963a1b57ad0ee3c68ced4f2d7f074f927f
otasigcheck: set verification package to com.android.htmlviewer

We need to use something that will always be there and not replaced
by other packages.

Change-Id: Ide942865f284239ae2ae2503005ccc7e8272995c
otasigcheck: include multi-digit cert indices

If the cert index is greater than 9, we still want to include it.

Change-Id: I82787e59557ae0bb7f15da16630d2b0afb7cff06