client: reencode cap releases for each request

client: reencode cap releases for each request

I think commit f7170f9 was based on some of my bad advice.  Every time the
client sends a request, it should look at what caps it has that might
conflict with the operation and (if possible) release them with the
request.  I suspect I was confusing this with the case on the MDS side of
things where we only process the release(s) when we first receive the
message and not when it is deferred/retried.

Specifically, this fixes a problem where we send a request to mds A and
release some set of caps, A tells us to talk to B instead, and we resend
the same message with (old, now bogus) releases intended for A to B
instead, where they probably make no sense.

Signed-off-by: Sage Weil <sage.weil@dreamhost.com>