Gazebo v9.8 crashes due to undefined symbol in libgazebo.so.9

[Kunal Tyagi]

When I upgraded Gazebo version by that, gazebo doesn't work.

```
# ref : http://gazebosim.org/tutorials?tut=install_ubuntu&cat=install
$ curl -sSL http://get.gazebosim.org | sh

$ gazebo -v
gazebo: symbol lookup error: /usr/lib/x86_64-linux-gnu/libgazebo_common.so.9: undefined symbol: _ZN8ignition10fuel_tools12ClientConfig12SetUserAgentERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE

```

The cause was that the following file's
 /usr/lib/x86_64-linux-gnu/libgazebo_common.so.9 uses libignition-fuel_tools1.so.1.
 After modified that part to libignition-fuel_tools2.so.2 in libgazebo_common.so.9,
 gazebo -v works, but it didn't work gazebo command.

We have workaround to run gazebo by the following command.

$ LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libignition-fuel_tools2.so.2 gazebo

[Jochen Sprickerhof (v-launchpad-jochen-sprickerhof-de)]

This is not a problem with the Ubuntu version.