generic: add missing $FSX_AVOID to fsx invocations

generic: add missing $FSX_AVOID to fsx invocations

generic/455 fails when run on an ext4 bigalloc file system.  Its
fsx invocations can make insert range and collapse range calls whose
arguments are not cluster aligned, and ext4 will fail those calls for
bigalloc.  They can be suppressed by adding the FSX_AVOID environment
variable to the fsx invocation and setting its value appropriately in
the test environment, as is done for other fsx-based tests.  This
avoids the need to exclude the test to avoid failures and makes it
possible to take advantage of the remainder of its coverage.

[ Also fix generic/457, as requested by Dave Chinner -- TYT]

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>