fvp_utils.sh: Double-quote interactive "command" keys for LAVA jobs

Command content may include escapes like "\r", and these must be included
in properly quoted strings in YAML syntax to work as expected.

This issue was found while working with lava-expect/spm-edk2-uart0.exp
script.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I603b1ed9cfa6dba6058c632c46ca5ce4ff40dc6c
1 file changed