eeschema: BUS definition doubled on copy/paste of child sheet

[Dino Ghilardi]

When a child sheet is copied, its bus definitions are doubled in memory.

To reproduce the behaviour:
-Create a new child sheet
-enter the child sheet
-create a bus definition using tools->bus definitions
-Go up one level to the parent sheet
-copy and paste the child sheet to have two of them
-open tools->bus definitions and now there are two definitions for the same bus, belonging to the same schematic file.

Saving, exiting and reopening the schematic "solves" the problem (the definition is back to one, the last created).

Possible data lost: if the first of the two definitions is modified and different from the second, changes are overwritten by the second while saving and closing the schematic.

----------------------------------------------------------------------

Application: Eeschema
Version: (5.1.0-843-gcb83f8acd), release build
Libraries:
    wxWidgets 3.0.2
    libcurl/7.52.1 OpenSSL/1.0.2r zlib/1.2.8 libidn2/0.16 libpsl/0.17.0 (+libidn2/0.16) libssh2/1.7.0 nghttp2/1.18.1 librtmp/2.3
Platform: Linux 4.9.0-8-amd64 x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.62.0
    OpenCASCADE Community Edition: 6.8.0
    Curl: 7.52.1
    Compiler: GCC 6.3.0 with C++ ABI 1010

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=OFF
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[KiCad Janitor (kicad-janitor)]

Fixed in revision 1721cc170004b5122437b7dbc626e6850531aeb0
https://git.launchpad.net/kicad/patch/?id=1721cc170004b5122437b7dbc626e6850531aeb0