Stop VM on ENOSPC error. (Gleb Natapov)

Stop VM on ENOSPC error. (Gleb Natapov)

This version of the patch adds new option "werror" to -drive flag.
Possible values are:

report    - report errors to a guest as IO errors
ignore    - continue as if nothing happened
stop      - stop VM on any error and retry last command on resume
enospc    - stop vm on ENOSPC error and retry last command on resume
            all other errors are reported to a guest.

Default is "report" to maintain current behaviour.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6388 c046a42c-6fe2-441c-8c8c-71466251a162