Disable caching start-time for all clocktypes except GPR_CLOCK_MONOTONIC

Caching the start-time for GPR_CLOCK_REALTIME has been causing errors in
cases where the system time is changed (after caching the time). In such
cases, the following functions produce incorrect results (and are off by
how much ever the system time was changed)
  grpc_millis_to_timespec() and grpc_timespec_to_millis_round_down()

This can cause problems especially when using the above functions to
get timer deadlines or completion queue timeouts.
(In the worst case scenarios, the timeouts/deadlines will always occur (if the
timeout inverval / deadline was less than the system change delta)

Ideally we should be reverting https://github.com/grpc/grpc/pull/11866
but since that is a large change (which introduced new APIs in
exec_ctx.cc), I am doing this change to effectively revert to the old
behavior (while still keeping the new APIs introduced in exec_ctx)

0 files changed, 0 insertions, 0 deletions