misc/ios: inject the -u device_id option before any other arguments
misc/ios: inject the -u device_id option before any other arguments

The idevicedebugserverproxy command takes a port number without a
flag, like so:

idevicedebugserverproxy 3222

If the -u <device_id> flag is added afterwards, it is ignored and
the command use an arbitrary device. Instead, always inject the -u
flag before any other idevice command arguments.

While here, also kill any leftover idevicedebugserverproxy instance
previous (failed) runs might have left running.

Change-Id: I0bf06ed1a20ef225abeca183f9ba8f396662d435
Reviewed-on: https://go-review.googlesource.com/112216
Run-TryBot: Elias Naur <993af7099cb24ce1a88d64108ae1e8b0385f2fc0@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

josharian/go,josharian/go,golang/go,akutz/go,CAFxX/go,josharian/go,nawawi/go,golang/go,nawawi/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,cloudflare/go,akutz/go,nawawi/go,akutz/go,nawawi/go,CAFxX/go,josharian/go,nawawi/go,cloudflare/go,CAFxX/go,josharian/go,golang/go,CAFxX/go,akutz/go,akutz/go,CAFxX/go,golang/go,josharian/go,josharian/go,akutz/go,cloudflare/go,golang/go,CAFxX/go,akutz/go,cloudflare/go,cloudflare/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,nawawi/go,CAFxX/go,josharian/go,golang/go,akutz/go