Limit number of tries to create alternate VHD blob names.
Limit number of tries to create alternate VHD blob names.

Signed-off-by: Quentin Pradet <d17611fde61d73f8de1b8b01bc47d446558ccd8e@apache.org>

Kami/libcloud,Scalr/libcloud,apache/libcloud,pquentin/libcloud,StackPointCloud/libcloud,mistio/libcloud,pquentin/libcloud,vongazman/libcloud,StackPointCloud/libcloud,vongazman/libcloud,Kami/libcloud,vongazman/libcloud,StackPointCloud/libcloud,andrewsomething/libcloud,Kami/libcloud,Scalr/libcloud,ByteInternet/libcloud,mistio/libcloud,apache/libcloud,pquentin/libcloud,andrewsomething/libcloud,mistio/libcloud,andrewsomething/libcloud,apache/libcloud,Scalr/libcloud,ByteInternet/libcloud,ByteInternet/libcloud