Werk #5584: Fixed exception when "Export List of Software packages as CSV file" is enabled

When having the export of the software packages list via CSV enabled while execution of the HW/SW inventory, an exception could happen in case the inventory data contained special characters. The exception looked like this on the command line:

Traceback (most recent call last):
  File "/omd/sites/stable/share/check_mk/modules/check_mk.py", line 4811, in <module>
    do_inv(hostnames)
  File "/omd/sites/stable/share/check_mk/modules/inventory.py", line 180, in do_inv
    do_inv_for(hostname)
  File "/omd/sites/stable/share/check_mk/modules/inventory.py", line 267, in do_inv_for
    run_inv_export_hooks(hostname, g_inv_tree)
  File "/omd/sites/stable/share/check_mk/modules/inventory.py", line 383, in run_inv_export_hooks
    inv_export[hookname]["export_function"](hostname, params, tree)
  File "/omd/sites/stable/share/check_mk/inventory/export_software_csv", line 67, in inv_export_software_csv
    out.write("%s\n" % separator.join(line))
UnicodeEncodeError: 'ascii' codec can't encode character u'\xf6' in position 1: ordinal not in range(128)

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