recipetool: Setup logging before calling prepare

recipetool: Setup logging before calling prepare

This avoids test failures like:

======================================================================
ERROR [0.946s]: test_recipetool_load_plugin (recipetool.RecipetoolTests)
INFO - ----------------------------------------------------------------------
INFO - Traceback (most recent call last):
  File "/media/build1/poky/meta/lib/oeqa/core/decorator/__init__.py", line 32, in wrapped_f
    return func(*args, **kwargs)
  File "/media/build1/poky/meta/lib/oeqa/selftest/cases/recipetool.py", line 514, in test_recipetool_load_plugin
    with open(srcfile) as fh:
FileNotFoundError: [Errno 2] No such file or directory: 'NOTE: Starting bitbake server...\n/media/build1/poky/meta-selftest/lib/recipetool/bbpath.py'
INFO - ----------------------------------------------------------------------

which comes from:

$ recipetool --quiet pluginfile
NOTE: Starting bitbake server...
/media/build1/poky/meta-selftest/lib/recipetool/bbpath.py

since there is corruption in the output despite the --quiet option. Setting
the logging up before calling tinfoil.prepare() resolves this.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>