binman: Use bintool wrappers for PKCS#11 tools in tests

binman: Use bintool wrappers for PKCS#11 tools in tests

The PKCS#11 signing tests in ftest.py call tools.run('softhsm2-util', ...)
directly (and the equivalent for pkcs11-tool and p11-kit), even though
the test setup has already constructed the corresponding Bintool
instances. As Quentin Schulz observed on v1, the bintool wrapper for
these tools is currently used only as an "is this installed?" probe.

Route the eight remaining call sites in ftest.py through
<bintool>.run_cmd(...), which the Bintool base class already provides.
The change is test-side only; no production binman code calls these
tools.

Suggested-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Simon Glass <sjg@chromium.org>