meta/lib/oe/terminal.py: Don't pass non-supported '--disable-factory' flag to gnome...

meta/lib/oe/terminal.py: Don't pass non-supported '--disable-factory' flag to gnome-terminal

By default, all GNOME terminals share a single process,
reducing memory usage.  This can be disabled by starting gnome-terminal
with the --disable-factory option

However, gnome-terminal in Fedora 20 does no longer support the
'--disable-factory' flag, so remove it. As the support for 'mate' terminals was
added as a copy of the gnome code in 8cc078a9c679845464c59028f584d7aba098cc1f,
remove the flag here aswell.

(From OE-Core rev: e8dca725ed8211a874472300a3ed50e494039ab9)

Signed-off-by: Jacob Kroon <jacob.kroon@mikrodidakt.se>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>