Store configuration file in repmgr.nodes table

When executing repmgr on remote nodes, we otherwise end up jumping
through hoops as we can't make assumptions about where the configuration
file is located, but really need to be able to provide it.

From a support point of view it will also make life easier as it will
be easy to specify exactly which file to provide.

configfile.c

@@ -11,7 +11,7 @@
 #include "log.h"
 
 const static char *_progname = NULL;
-static char config_file_path[MAXPGPATH];
+char config_file_path[MAXPGPATH] = "";
 static bool config_file_provided = false;
 bool config_file_found = false;