Prevent jdk_switcher from resetting PATH

Since `/etc/profile.d/load_jdk_switcher.sh` always sources
`$HOME/.jdk_switcher_rc`, jdk_switcher reverting to the original `$PATH`
causes problems when other stuff (such as PostgreSQL service)
starts a login shell after manipulating `$PATH` and subshell is expected
to find stuff in the modified `$PATH`.
```
$ PATH=foo:bar/
$ echo :$(echo $PATH: | sed -e 's_/*:_:_g'):
:foo:bar::
```

I think this'll work better:

```
PATH="$(echo :$PATH: | sed -e 's_/*:_:_g')"
```