Unify the comparison idioms use.
Always use `if(!strcmp())` for "if string equals"
and `if(strcmp())` for "if string is not equal".
Never use `== 0` and `!= 0` with `strcmp()`.
Minor reformatting of the code immediately surrounding the
refactored lines.
Resolvesipmitool/ipmitool#104
Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>