fish: Change test-escapes so test is not endian-sensitive.

The test used the external 'od' command to compare the output of
guestfish with what it's supposed to be.  Unfortunately by default
this outputs groups of 2-byte words, with the words' endianness
affected by the current hardware endianness.  For example:

x86-64$ echo -n ab | od
0000000 061141
0000002

ppc64$ echo -n ab | od
0000000 060542
0000002

By using 'od -b' instead we can output bytes instead of words, and
there is no endianness issue, and the output is clearer:

x86-64$ echo -n ab | od -b
0000000 141 142
0000002

ppc64$ echo -n ab | od -b
0000000 141 142
0000002

0 files changed, 0 insertions, 0 deletions