[Bluetooth] remove glib mainloop thread

Following XWALK-1331 bug resolution which consists of reintroducing
a glib mainloop running in Extesion Process. As a consequence, there
is no need to make run a glib mainloop in separate crosswalk extensions.
Merge pull request #355 from eurogiciel-oss/remove_glib_mainloop

[Bluetooth] remove glib mainloop thread