Exiting American Idol judge Katy Perry isn’t trying to hide that she’s over the singing competition show. While Perry turned on the charm for the cameras during a recent taping, her behavior behind the scenes was said to be a different story. A source said she stayed “glued to her phone” and “coldly ignored” the audience during commercial breaks, RadarOnline.com has learned. According to an insider, the I Kissed a Girl singer’s behavior on set was shockingly different during commercial breaks. “It was off-putting to see how she was so into her phone and ignored fans who were shouting her name,…