By Piya Sinha-Roy LOS ANGELES (Reuters) - Country singer Kenny Chesney landed his seventh No. 1 album on the weekly Billboard 200 album chart on Wednesday with his latest record "Life on a Rock." The album sold 153,000 copies in its first week, according to figures from Nielsen SoundScan, giving Chesney the second-most No. 1 country albums, behind Garth Brooks. Last week's chart-topper, Michael Buble's "To Be Loved" slipped to No. 2, while Justin Timberlake's "The 20/20 Experience" held steady at No. 3 for the fourth consecutive week. ...