JTAG: 'is_slave' is not always present

This fix a crash when booting JTAG devices.

Change-Id: I6833a1eac194d60d73a0386dcdeb882649087184
qemu-aarch64: add proper networking options

Change-Id: I234bfeff7472a331f9adbe71f1089cc78593dc41
Merge branch 'master' into staging