Description of problem:
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When a brick is full, files are not getting migrated at all.
I created a hot tier with 2x2 with each brick of 1GB size. That means effectively the hot tier is of 2GB size.
I started to create a file of 1.5GB using dd command, which was getting created on 1st brick. But as the 1GB gets filled, the new file stops to grow with below error:
dd: error writing ‘zerobyte.50’: Input/output error
dd: closing output file ‘zerobyte.50’: Input/output error

Now the file is not getting demoted at all and hence no more writes are going to the hot tier.

Similarly, if i fill the other brick too, then it essentially means that the whole hot tier is full.

In this case, no more new creates are being allowed even to the cold tier (also refer bz#1259312)

Version-Release number of selected component (if applicable):
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glusterfs-server-3.7.5-0.18.git2def6bb.el7.centos.x86_64






Steps to Reproduce:
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1.create a 2x2 vol and start it
2.attach a tier of 2x2 with limited size, say each brick of 1GB.
Also turn on ctr (note in this case quota was not turned on)
3.Now create a file of 1.5GB such that it goes to one of the hot bricks
It will fail after it creates 1GB
4. Now this file doesnt get demoted at all 
5.Now again create a 1.5GB file such that it goes to the other hot brick(to make hot layer full)
5. Now file doenst get demoted at all



Expected results:
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File must get demoted once it is old and idle