[LTP] [PATCH v3] Add tst_dev_block_size utility

[Cyril Hrubis]

Hi!
Pushed with a few fixes for the test, thanks.

Actually the LOOP_SET_BLOCK_SIZE ioctl() may fail with EAGAIN if there
are dirty blocks on the loop device and as a matter of the fact it did
fail for me in a few cases when I executed the test several times. I
guess that it all boils down to how the backing file is preallocated,
and there are several different options for that...

Anyways I fixed that part by adding the LTP retry wrapper around the
ioctl() which makes the test succeed repeatedly.

+ removed the mode for SAFE_OPEN() which is useless without O_CREAT
+ removed needs_tmpdir which is implied by needs_device

-- 
Cyril Hrubis
chrubis@suse.cz