Exclude field 'group' when on image report form.
Exclude field 'group' when on image report form.

Fixes bug 1637 (https://bugs.linaro.org/show_bug.cgi?id=1637).

Change-Id: I46c78f31b8ec6b4519fab5e3c5a0a068eabfaaaa

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server