Revert "meta: replace os.popen with subprocess.Popen"

Revert "meta: replace os.popen with subprocess.Popen"

This reverts commit e83d8e58a6b107eea87df0ec233a1bc932b2c6e as the conversion
is not correct. Its replacing readlines() calls which generate an array with
what are effectively strings. There are split("\n") calls missing in many
cases so this needs to be reverted until it gets fixed.