Add the repository name prefix to release test environment

This test is now failing on ci.bazel.io

--
MOS_MIGRATED_REVID=120328587
diff --git a/scripts/release/testenv.sh b/scripts/release/testenv.sh
index e5debf2..d00ea64 100755
--- a/scripts/release/testenv.sh
+++ b/scripts/release/testenv.sh
@@ -19,7 +19,7 @@
 [ -z "$TEST_SRCDIR" ] && { echo "TEST_SRCDIR not set!" >&2; exit 1; }
 
 # Load the unit-testing framework
-source "${TEST_SRCDIR}/src/test/shell/unittest.bash" || \
+source "${TEST_SRCDIR}/io_bazel/src/test/shell/unittest.bash" || \
   { echo "Failed to source unittest.bash" >&2; exit 1; }
 
 # Commit at which we cut the master to do the test so we always take the git