lxc/start.c: Fix legacy PR_{G,S}ET_NO_NEW_PRIVS handling
lxc/start.c: Fix legacy PR_{G,S}ET_NO_NEW_PRIVS handling

The configure checks for these use AC_CHECK_DECLS, which define the symbol
to 0 if not available - So adjust the code to match.  From the autoconf
manual:

https://www.gnu.org/software/autoconf/manual/autoconf-2.65/html_node/Generic-Declarations.html)

For each of the symbols (comma-separated list), define HAVE_DECL_symbol (in
all capitals) to ‘1’ if symbol is declared, otherwise to ‘0’.

Signed-off-by: Peter Korsgaard <4b8373d016f277527198385ba72fda0feb5da015@korsgaard.com>

caglar10ur/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,hallyn/lxc,hallyn/lxc,thmo/lxc,thmo/lxc,hallyn/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,thmo/lxc