virNetServerClientNewPostExecRestart: Avoid align problems

virNetServerClientNewPostExecRestart: Avoid align problems

I've noticed this while trying to compile libvirt on my arm box.

  CC       rpc/libvirt_net_rpc_server_la-virnetserverclient.lo
rpc/virnetserverclient.c: In function 'virNetServerClientNewPostExecRestart':
rpc/virnetserverclient.c:516:45: error: cast increases required alignment of target type [-Werror=cast-align]
                                             (long long *) &timestamp) < 0) {
                                             ^
cc1: all warnings being treated as errors

Problem is, @timestap is defined as time_t which is 32 bits long,
and we are typecasting it to long long which is 64bits long.
Solution is to make @timestamp type of long long. At the same
time, we can make @conn_time in _virNetServerClient struct long
long too. There is no need for it to be type of time_t.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>