Refactor status printing.

Try to use a POOL_MEM whenever possible so we also don't make mistakes
in the length of the status string a possibly overrun an string. Also
if we don't print a string because of being in API mode it doesn't make
sense to even build the status string (as we are not going to print it
anyway.) Also fixes 2 other Coverity high impatct bugs.

src/dird/catreq.c

@@ -670,6 +670,7 @@ bool despool_attributes_from_file(JCR *jcr, const char *file)
                   be.bstrerror());
             goto bail_out;
          }
+         msg[nbytes] = '\0';
          size += nbytes;
       }
       if (!jcr->is_job_canceled()) {