Don't store UID & GID persistently in the context structure

c->uid and c->gid are first set in conf(), and last used in check_root()
itself called from conf().  Therefore these don't need to be fields in the
long lived context structure and can instead be locals in conf().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

passt.h

@@ -144,8 +144,6 @@ struct ip6_ctx {
  * @sock_path:		Path for UNIX domain socket
  * @pcap:		Path for packet capture file
  * @pid_file:		Path to PID file, empty string if not configured
- * @uid:		UID we should drop to, if started as root
- * @gid:		GID we should drop to, if started as root
  * @pasta_netns_fd:	File descriptor for network namespace in pasta mode
  * @pasta_userns_fd:	Descriptor for user namespace to join, -1 once joined
  * @netns_only:		In pasta mode, don't join or create a user namespace
@@ -198,9 +196,6 @@ struct ctx {
 	char pcap[PATH_MAX];
 	char pid_file[PATH_MAX];
 
-	uid_t uid;
-	uid_t gid;
-
 	int pasta_netns_fd;
 	int pasta_userns_fd;
 	int netns_only;