Fix problem with --showcmd and callbacks that verify

David reports:

I'm using "fio --showcmd file.job" to convert a script to plain
commandline arguments and this fails if the directory specified in job
file does not exist. While this has to be an error if the job is being
executed, it should not be in context of --showcmd.

To reproduce:
$ cat job.fio
[global]
directory=/x

$ fio --showcmd job.fio
fio: /x is not a directory
fio: failed parsing directory=/x
fio: job global dropped

Expected output:
fio --directory=/x

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fio.h b/fio.h
index e7d5c27..0d7fbeb 100644
--- a/fio.h
+++ b/fio.h
@@ -420,6 +420,7 @@
 extern void add_job_opts(const char **, int);
 extern char *num2str(unsigned long, int, int, int, int);
 extern int ioengine_load(struct thread_data *);
+extern int parse_dryrun(void);
 
 extern uintptr_t page_mask;
 extern uintptr_t page_size;