client:

- Fixed problem that check for missing --enable-async-writes parameter was always true (unlike default_value, implicit_value does not put the option in the "vm" map unless it's actually set).
- Renamed "kB" to "kb" since the command line arguments are case sensitive.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@3608 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534