Fix tests for pt-fk-error-logger

$ prove -vw --trap --timer t/pt-fk-error-logger
...
[17:46:32] t/pt-fk-error-logger/basics.t ........ 
ok 1 - Prints fk error by default
ok 2 - No output with --quiet
ok 3 - Saved foreign key error timestamp
ok 4 - Saved foreign key error
ok 5 - Doesn't save same error twice
ok 6 - Still only 1 saved error
ok 7 - Second foreign key error
ok 8 - Now 2 saved errors
ok 9 - Print foreign key error
ok 10 - No foreign key errors, no errors, no output (bug 1075773)
not ok 11 - Dies if PID file already exists (--pid without --daemonize) (issue 391)

#   Failed test 'Dies if PID file already exists (--pid without --daemonize) (issue 391)'
#   at t/pt-fk-error-logger/basics.t line 194.
#                   'Can't locate object method "make_PID_file" via package "Daemon" at /home/sveta/src/percona-toolkit/bin/pt-fk-error-logger line 4197.
# '
#     doesn't match '(?^:PID file /tmp/pt-fk-error-log-test-113995.pid already exists)'
ok 12 - Sandbox servers
1..12
# Looks like you failed 1 test of 12.
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/12 subtests