block: enable testing of LUKS driver with block I/O tests

This adds support for testing the LUKS driver with the block
I/O test framework.

   cd tests/qemu-io-tests
   ./check -luks

A handful of test cases are modified to work with luks

 - 004 - whitelist luks format
 - 012 - use TEST_IMG_FILE instead of TEST_IMG for file ops
 - 048 - use TEST_IMG_FILE instead of TEST_IMG for file ops.
         don't assume extended image contents is all zeros,
         explicitly initialize with zeros
         Make file size smaller to avoid having to decrypt
         1 GB of data.
 - 052 - don't assume initial image contents is all zeros,
         explicitly initialize with zeros
 - 100 - don't assume initial image contents is all zeros,
         explicitly initialize with zeros

With this patch applied, the results are as follows:

  Passed: 001 002 003 004 005 008 009 010 011 012 021 032 043
          047 048 049 052 087 100 134 143
  Failed: 033 120 140 145
 Skipped: 007 013 014 015 017 018 019 020 022 023 024 025 026
          027 028 029 030 031 034 035 036 037 038 039 040 041
          042 043 044 045 046 047 049 050 051 053 054 055 056
          057 058 059 060 061 062 063 064 065 066 067 068 069
          070 071 072 073 074 075 076 077 078 079 080 081 082
          083 084 085 086 087 088 089 090 091 092 093 094 095
          096 097 098 099 101 102 103 104 105 107 108 109 110
          111 112 113 114 115 116 117 118 119 121 122 123 124
          128 129 130 131 132 133 134 135 136 137 138 139 141
          142 144 146 148 150 152

The reasons for the failed tests are:

 - 033 - needs adapting to use image opts syntax with blkdebug
         and test image in order to correctly set align property
 - 120 - needs adapting to use correct -drive syntax for luks
 - 140 - needs adapting to use correct -drive syntax for luks
 - 145 - needs adapting to use correct -drive syntax for luks

The vast majority of skipped tests are exercising code that is
qcow2 specific, though a couple could probably be usefully
enabled for luks too.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1462896689-18450-4-git-send-email-berrange@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
