tcl: fix potential memory leaks

Reorder to allocate all memory after COMMAND_PARSE_NUMBER call.
This removes a clang warning about un-released memory

Change-Id: I8dbeb664a6467077157015bd879bc0aefc5e8614
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/776


Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>