tests: allow non-inotify tailf to keep up

When tailf is not using inotify, it seems to sleep for 0.25s between
checks. Just giving a 0.1s time window between update and removal of the
input file thus gives little chance for tailf to succeed.
Similar between startup and append to file, make sure initial
content is read before appending additional data by bumping the time.

This should possibly be bumped much larger to make sure that
the tailf process actually gets a chance to run at all in the
given time window. Otherwise it might fail on really slow/overloaded
machines.
The drawback would then ofcourse be to increase the time it takes
to run the testsuite.

Signed-off-by: Andreas Henriksson <andreas@fatal.se>