Pin version of dogpile

Force dogpile to a static version as 1.0.0, released July 19, 2020
is not compatible with the version of stevedore that we use.

Change-Id: Icc2758e07bafa935bf4403bd5735b47e79b4bc66
Signed-off-by: beierlm <mark.beierl@canonical.com>
(cherry picked from commit 90d4e9e5)