test-install: Use lxc-destroy -f instead of lxc-stop.
test-install: Use lxc-destroy -f instead of lxc-stop.

Fixes this error after rebooting the host:

$ sudo ./destroy-all  -f
zulip-install-bionic-41MM2
lxc-stop: zulip-install-bionic-41MM2: tools/lxc_stop.c: main: 191 zulip-install-bionic-41MM2 is not running

Signed-off-by: Anders Kaseorg <dfdb7392591db597bc41cf266a9c3bc12a2706e5@zulipchat.com>

showell/zulip,kou/zulip,punchagan/zulip,kou/zulip,brainwane/zulip,shubhamdhama/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,hackerkid/zulip,brainwane/zulip,rht/zulip,rht/zulip,timabbott/zulip,brainwane/zulip,zulip/zulip,brainwane/zulip,shubhamdhama/zulip,eeshangarg/zulip,andersk/zulip,brainwane/zulip,eeshangarg/zulip,timabbott/zulip,timabbott/zulip,rht/zulip,synicalsyntax/zulip,hackerkid/zulip,shubhamdhama/zulip,showell/zulip,showell/zulip,rht/zulip,eeshangarg/zulip,timabbott/zulip,shubhamdhama/zulip,rht/zulip,showell/zulip,synicalsyntax/zulip,rht/zulip,showell/zulip,andersk/zulip,punchagan/zulip,synicalsyntax/zulip,punchagan/zulip,shubhamdhama/zulip,andersk/zulip,brainwane/zulip,kou/zulip,synicalsyntax/zulip,synicalsyntax/zulip,zulip/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,kou/zulip,brainwane/zulip,eeshangarg/zulip,showell/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,eeshangarg/zulip,timabbott/zulip,andersk/zulip,shubhamdhama/zulip,timabbott/zulip,andersk/zulip,shubhamdhama/zulip,zulip/zulip,kou/zulip,synicalsyntax/zulip,hackerkid/zulip,zulip/zulip,hackerkid/zulip,zulip/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,timabbott/zulip,showell/zulip,andersk/zulip,synicalsyntax/zulip,punchagan/zulip