ipvs: add missing ip_vs_pe_put in sync code

ip_vs_conn_fill_param_sync() gets in param.pe a module
reference for persistence engine from __ip_vs_pe_getbyname()
but forgets to put it. Problem occurs in backup for
sync protocol v1 (2.6.39).

Also, pe_data usually comes in sync messages for
connection templates and ip_vs_conn_new() copies
the pointer only in this case. Make sure pe_data
is not leaked if it comes unexpectedly for normal
connections. Leak can happen only if bogus messages
are sent to backup server.

Fixes: fe5e7a1e ("IPVS: Backup, Adding Version 1 receive capability")
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>