tools: Let adb secure check depend on "==0" rather than "!=1"

We are using PRODUCT_SYSTEM_DEFAULT_PROPERTIES to set
`ro.adb.secure` property. But unfortunately this flag only
affect system partition, which means in other partitions
e.g. vendor and system_ext `ro.adb.secure` stays empty.
Thus `persist.sys.usb.config=adb` is unconditionally set
in partitions other than system, which lead to adb enabled
by default even on user build.

Change-Id: I1f8b463b3ec645309369f36014bed556e75ed210
Signed-off-by: LibXZR <i@xzr.moe>