Suppress some bash redirection error messages

Suppress some bash redirection error messages

In particular, when testing if the filesystem allows tabs in
filenames, bash issues an error something like:

./t4016-diff-quote.sh: pathname	with HT: No such file or directory

which is caused by the failure of the (stdout) redirection,
since the file cannot be created. In order to suppress the
error message, you must redirect stderr to /dev/null, *before*
the stdout redirection on the command-line.

Also, remove a redundant filesystem check from the begining of
the t3902-quoted.sh test and standardise the "test skipped"
message to 'say' on exit.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>