test: Add test_send_caps_error_before_connected to usb_pe_drp
test: Add test_send_caps_error_before_connected to usb_pe_drp

Add a test for the other half of handling an error on sending
source capabilities. Before connection, PE_SRC_Send_Capabilities
goes to PE_SRC_Discovery on send error. Once connected, to goes
to PE_Send_Soft_Reset.

BUG=b:161835483
BRANCH=none
TEST=make run-usb_pe_drp

Signed-off-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>
Change-Id: I92df9159286536bdda76e5b8530494c6aa368af1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2553344
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec