The function that runs to compress a stacked mirror after

The function that runs to compress a stacked mirror after
converting from 2-way to 3-way mirror (collapse_mirrored_lv)
was calling '_remove_mirror_images' with the 'remove_log'
parameter set.  When the code was put in to fix 599898 to
honor log parameters during conversion, this argument was
suddenly being honored.  Thus, when someone would convert from
a 2-way to 3-way mirror, the log would get removed.

'collapse_mirrored_lv' should not be calling '_remove_mirror_images'
with 'remove_log' set.