Skip flakky tests

Skip flakky tests

Initially (2023-02-15):
 - TestAPICSendMetrics
 - TestLongRunningQPS

Both aim at checking performance, and might error out when the underlying
system is “slow”. That was the case for the first test on arm64 (KO on
arm-arm-01, OK on arm-ubc-03) and on armel (KO on arm-ubc-06, OK on
arm-conova-02), and for the second test on mipsel (KO on mipsel-aql-02).

The same might happen on ci.debian.net, so disable both tests everywhere.

Extension (2023-03-01):
 - TestAPICCAPIPullIsOld
 - TestAPICHandleDeletedDecisions
 - TestAPICPullTop
 - TestGetDecisionsSinceCount

Gbp-Pq: Name 0013-skip-flakky-tests.patch