tests: fix resize test tmpfs max-file-size checking

tests: fix resize test tmpfs max-file-size checking

Old distros may not have the "truncate" tool, so use "dd" instead.

If tmpfs cannot handle a 2GB temp file (e.g. old RHEL5 and SLES 11
kernels) then skip the test instead of failing it.  If this fails,
try to report better error messages instead of failing silently.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>