Add diagnostic option "repmgr node check --has-passfile"

This checks if the active libpq version (9.6 and later) has the
"passfile" option, and returns 0 if present, 1 if not.
`

dbutils.c

@@ -700,7 +700,7 @@ has_passfile(void)
 
 	PQconninfoFree(defs);
 
-    return has_passfile;
+	return has_passfile;
 }