Allow generating GMR report upon file trigger in addition to a signal.
The feature has been available in oslo.reports since 1.11.0[1] but it
can't be used in octavia without proper initialization.
[1] d23e0a65b23dc77d0104075d2313de6ca22b5cae
Change-Id: Ifa08d1175a696263fea2c0e434f1e8e4d76395fe
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>