Description of problem:
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Empty string is an acceptable value for the volume option "auth.allow". When we set the option auth.allow to empty string, upon subsequent restart of glusterd, glusterd doesn't get started. 

The following is seen in the logs - 
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[2012-09-24 17:19:49.760116] E [glusterd-store.c:1526:glusterd_store_validate_key_value] 0-glusterd: Glusterd store may be corrupted, Invalid value (null) for key auth.allow in /var/lib/glusterd/vols/Test/info
[2012-09-24 17:19:49.760129] E [glusterd-store.c:2184:glusterd_store_retrieve_volumes] 0-: Unable to restore volume: Test

The following are the contents of info - 
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type=0
count=2
status=0
sub_count=0
stripe_count=1
replica_count=1
version=2
transport-type=0
volume-id=ec8e5705-4a3c-4fa5-940e-f67eae32112c
username=229884d6-c11b-4b88-9a49-9faea433f525
password=807bf0cc-2e1c-433a-85a0-d61225839851
auth.allow=
brick-0=10.70.1.137:-export1-Test-brick1
brick-1=10.70.1.137:-export2-Test-brick2

Version-Release number of selected component (if applicable):
glusterfs 3.3.0

How reproducible:
Always reproducible

Steps to Reproduce:
1.Create a gluster volume 
2.gluster volume set <vol_name> auth.allow ""
3.Restart glusterd
4.On running ps aux | grep glusterd, glusterd is not seen
  
Actual results:
glusterd does not start

Expected results:
glusterd should start

Additional info: