Mynewt: Partial fix for bootutil unit test
Mynewt: Partial fix for bootutil unit test

The bootutil unit tests fail to build with the following error:

    Testing package @mcuboot/boot/bootutil/test
    Unsatisfied APIs detected:
        * log, required by: sys/log/modlog

This commit adds a `sys/log/stub` dependency to the bootutil unit test
package.

NOTE: This unit test package still fails to build because the code is
out of date.  This commit just fixes one of several issues.

Signed-off-by: Christopher Collins <931fdb982a80bb744c6b95a3e1cdb3f421ab63fd@apache.org>

runtimeco/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,ATmobica/mcuboot,tamban01/mcuboot,runtimeco/mcuboot,utzig/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,runtimeco/mcuboot,utzig/mcuboot,utzig/mcuboot,utzig/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,utzig/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,tamban01/mcuboot,runtimeco/mcuboot