By Scott DiSavino (Reuters) -U.S. energy firms this week added oil and natural gas rigs for a fourth week in a row for the first time since February, energy services firm Baker Hughes said in its closely followed report on Friday. The oil and gas rig count, an early indicator of future output, rose by seven to 549 in the week to September 26, its highest since June. Despite this week's rig increase, Baker Hughes said the total count was still down 38 rigs, or 6% below this time last year. Baker Hughes ...