vlib: improve exec path search

Fixes VPP invocation with relative path, i.e.:

$ bin/vpp unix interactive

Type: improvement
Change-Id: I0278710bb472b92e31389b2d28955c3d33550230
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vlib/main.h b/src/vlib/main.h
index 18ec3be..2581d49 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -220,7 +220,6 @@
   volatile u32 queue_signal_pending;
   volatile u32 api_queue_nonempty;
   void (*queue_signal_callback) (struct vlib_main_t *);
-  u8 **argv;
 
   /* Top of (worker) dispatch loop callback */
   void (**volatile worker_thread_main_loop_callbacks)
@@ -283,6 +282,12 @@
   /* Name for e.g. syslog. */
   char *name;
 
+  /* full path to main executable */
+  char *exec_path;
+
+  /* command line arguments */
+  u8 **argv;
+
   /* post-mortem callbacks */
   void (**post_mortem_callbacks) (void);