Minor changes to formatting. Added warning if P4ROOT_not_usable.txt is
found when starting in 'force_start' mode, but the server still attempts
Note: Unlike the journal corruption check, the 'force_start' option is
not mentioned in the error message to the user if the server
refuses to start due to ahving a P4ROOT_not_usable.txt file. This is
because potential journal corruption is something that can sometimes be
ignored, and in any case you may need to start the server to work on it.
But for the scenarios in which P4ROOT_not_usable.txt is there, e.g. a
checkpiont wasn't done replaying when 'load_checkpoint.sh' got interrupted,
force_start won't likely be helpful.