Update WifiP2pService.java

When station is connecting to AP i.e wifi state is either
connecting or obtaing ip address, Wi-Fi state machine will
send BLOCK_DISCOVERY event to P2P service manager and discovery
is postponed until DHCP success/failure. During this if we
receive DISCOVER_PEERS command then p2p service manager will
return discovery failure because "mDiscoveryPostponed"
variable is not getting updated properly due to improper
condition checking.

To mitigate this issue modified the conditions to update
the variable "mDiscoveryPostponed".