Changes

jenkins: build docs in virtualenv as well

The build system uses a virtual environment, in which it installs
pysim and its dependencies. This is done for the integration tests,
but not when building the sphinx documentation. However, the
documentation build process also invokes pysim code to generate
documentation from the docstrings. This means we need pysim with
all its dependencies for the doc building as well.

Change-Id: I6381eeef7fa19873ca0cc330a0ab43b7ef5096e4
Related: SYS#7094