network: consolidate connection count updates for device pool

network: consolidate connection count updates for device pool

networkReleaseActualDevice() and networkNotifyActualDevice() both were
updating the individual devices' connections count in two separate
places (unlike networkAllocateActualDevice() which does it in a single
unified place after success:). The code is correct, but prone to
confusion / later breakage. All of these updates are anyway located at
the end of if/else clauses that are (with the exception of a single
VIR_DEBUG() in each case) immediately followed by the success: label
anyway, so this patch replaces the duplicated ++/-- instructions with
a single ++/-- inside a qualifying "if (dev)" down below success:.
(NB: if dev != NULL, by definition we are using a device (either pci
or netdev, doesn't matter for these purposes) from the network's pool)

The VIR_DEBUG args (which will be replaced in a followup patch anyway)
were all adjusted to account for the connection count being out of
date at the time.