scripts/unit-test: Add stdplus

stdplus was added to the unit test docker but our unit-test script
should know how to recognize it even if it isn't in the caches.

Change-Id: I62dc94eb393d9749a1b51e80354a64fadbbc3393
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/scripts/unit-test.py b/scripts/unit-test.py
index 8f318e3..c1c3f85 100755
--- a/scripts/unit-test.py
+++ b/scripts/unit-test.py
@@ -700,6 +700,7 @@
             'blobs-ipmid': 'phosphor-ipmi-blobs',
             'sdbusplus': 'sdbusplus',
             'sdeventplus': 'sdeventplus',
+            'stdplus': 'stdplus',
             'gpioplus': 'gpioplus',
             'phosphor-logging/log.hpp': 'phosphor-logging',
         },
@@ -712,6 +713,7 @@
             'libipmid-host': 'phosphor-host-ipmid',
             'sdbusplus': 'sdbusplus',
             'sdeventplus': 'sdeventplus',
+            'stdplus': 'stdplus',
             'gpioplus': 'gpioplus',
             'phosphor-logging': 'phosphor-logging',
             'phosphor-snmp': 'phosphor-snmp',