Fix race condition in Cache.Clear

[martinmr]

There are race conditions when Set or Del are called at the same time
as Clear. Instead of creating a new channel, Clear now processes all the
entries from the channel.

Fixes #132

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This change is 

[manishrjain]

Reviewed 1 of 1 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @jarifibrahim, @karlmcguire, and @martinmr)

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cache.go, line 299 at r1 (raw file):

	// Swap out the setBuf channel.
	c.setBufLock.Lock()
	c.setBuf = make(chan *item, setBufSize)

Instead of make chan. I could do a for loop and empty the chan out.

Let's not use locks.

[martinmr]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @jarifibrahim, @karlmcguire, and @manishrjain)

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cache.go, line 299 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

Instead of make chan. I could do a for loop and empty the chan out.

Let's not use locks.

Done.

[manishrjain]

Merge this, if this works?

Reviewed 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @jarifibrahim and @karlmcguire)

[manishrjain]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @jarifibrahim and @karlmcguire)