fstrim: -17b

Also, use the name of the block device we found, not necessarily the one
we got from the user:
fstrim -v /
/dev/sdj: 4711 bytes were trimmed

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
fstrim: Indicate failure on error

+14b

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
fstrim: Needs to fire at the mp, not bd

It's a filesystem thing from this perspective.
+1b

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
fix bashisms in testsuite/

These places use ${var/search/replace}, $((n++) and
`type -p' constructs which are not-so-standard.
Replace with equivalent constructs.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>