Fix worksheet attachments viewlet

[toropok]

Description of the issue/feature this PR addresses

While Viewlet gathers analyses attachments it tries to call getRequestID() method on Reference Analysis entity. Such method does not exist and it raises exception:

Traceback (most recent call last):
  File "/home/senaite/buildout-cache/eggs/cp27mu/plone.app.viewletmanager-3.1.2-py2.7.egg/plone/app/viewletmanager/manager.py", line 110, in render
    html.append(viewlet.render())
  File "/home/senaite/senaitelims20/src/senaite.core/src/senaite/core/browser/viewlets/attachments.py", line 65, in render
    return self.template()
  File "/home/senaite/buildout-cache/eggs/cp27mu/Zope-4.6.3-py2.7.egg/Products/Five/browser/pagetemplatefile.py", line 126, in call
    return self.__func__(__self__, *args, **kw)
  File "/home/senaite/buildout-cache/eggs/cp27mu/Zope-4.6.3-py2.7.egg/Products/Five/browser/pagetemplatefile.py", line 61, in call
    sourceAnnotations=getattr(debug_flags, 'sourceAnnotations', 0),
  File "/home/senaite/buildout-cache/eggs/cp27mu/zope.pagetemplate-4.5.0-py2.7.egg/zope/pagetemplate/pagetemplate.py", line 135, in pt_render
    strictinsert=0, sourceAnnotations=sourceAnnotations
  File "/home/senaite/buildout-cache/eggs/cp27mu/Zope-4.6.3-py2.7.egg/Products/PageTemplates/engine.py", line 378, in call
    return template.render(**kwargs)
  File "/home/senaite/buildout-cache/eggs/cp27mu/z3c.pt-3.3.0-py2.7.egg/z3c/pt/pagetemplate.py", line 176, in render
    return base_renderer(**context)
  File "/home/senaite/buildout-cache/eggs/cp27mu/Chameleon-3.9.1-py2.7.egg/chameleon/zpt/template.py", line 302, in render
    return super(PageTemplate, self).render(**_kw)
  File "/home/senaite/buildout-cache/eggs/cp27mu/Chameleon-3.9.1-py2.7.egg/chameleon/template.py", line 215, in render
    raise_with_traceback(exc, tb)
  File "/home/senaite/buildout-cache/eggs/cp27mu/Chameleon-3.9.1-py2.7.egg/chameleon/template.py", line 192, in render
    self._render(stream, econtext, rcontext)
  File "/home/senaite/senaitelims20/var/cache/b6375fef815b0f20927932b53779f2c9.py", line 214, in render
    __value = _static_140306927250896('path', u'view/get_analyses', econtext=econtext)(_static_140306927276304(econtext, __zt_tmp))
  File "/home/senaite/buildout-cache/eggs/cp27mu/zope.tales-5.1-py2.7.egg/zope/tales/expressions.py", line 250, in call
    return self._eval(econtext)
  File "/home/senaite/buildout-cache/eggs/cp27mu/Zope-4.6.3-py2.7.egg/Products/PageTemplates/Expressions.py", line 225, in _eval
    return render(ob, econtext.vars)
  File "/home/senaite/buildout-cache/eggs/cp27mu/Zope-4.6.3-py2.7.egg/Products/PageTemplates/Expressions.py", line 155, in render
    ob = ob()
  File "/home/senaite/senaitelims20/src/senaite.core/src/senaite/core/browser/viewlets/attachments.py", line 122, in get_analyses
    analyses = map(self.get_analysis_info, analyses)
  File "/home/senaite/senaitelims20/src/senaite.core/src/senaite/core/browser/viewlets/attachments.py", line 130, in get_analysis_info
    sample_id = analysis.getRequestID()
AttributeError: 'RequestContainer' object has no attribute 'getRequestID'

Current behavior before PR

exception raised

Desired behavior after PR is merged

no exception

--
I confirm I have tested this PR thoroughly and coded it according to PEP8
and Plone's Python styleguide standards.