tests: remove unsupported qemu feature

pretty=on|off has been removed from qemu and its presence
causes VM boot up issues.

Type: fix

Change-Id: I4a9f15dba5015e81fbd32278b1c74b2606c32c8f
Signed-off-by: Naveen Joy <najoy@cisco.com>

test/scripts/run_vpp_in_vm.sh

@@ -171,7 +171,7 @@ _EOF_
                  -nodefaults \
                  -name test_$(basename $INIT) \
                  -chardev stdio,mux=on,id=char0 \
-                 -mon chardev=char0,mode=readline,pretty=on \
+                 -mon chardev=char0,mode=readline \
                  -serial chardev:char0 \
                  -machine pc,accel=kvm,usb=off,mem-merge=off \
                  -cpu host \