Improve coverage of vboot_api_init.c
Improve coverage of vboot_api_init.c

BUG=chromium-os:38139
BRANCH=none
TEST=make runtests

Change-Id: I3d39feb712eb7e572f9c57f27449f19e8e809ed0
Reviewed-on: https://gerrit.chromium.org/gerrit/41896
Commit-Queue: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Tested-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

coreboot/vboot,coreboot/vboot,marineam/seismograph,ionave/seismograph,ccaapton/vboot_reference,geekboxzone/mmallow_external_vboot_reference,geekboxzone/mmallow_external_vboot_reference,coreboot/vboot,ccaapton/vboot_reference,acorn-marvell/vboot_reference,ionave/seismograph,coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,marineam/seismograph,acorn-marvell/vboot_reference,acorn-marvell/vboot_reference,coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,ionave/seismograph,ccaapton/vboot_reference,acorn-marvell/vboot_reference,geekboxzone/mmallow_external_vboot_reference,marineam/seismograph,ccaapton/vboot_reference,marineam/seismograph