Fix tests for pt-deadlock-logger

$ prove -vw --trap --timer t/pt-deadlock-logger/
...
[17:34:33] t/pt-deadlock-logger/standard_options.t ..... 
ok 1 - Source DSN inherits from standard connection options (issue 248)
not ok 2 - 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-deadlock-logger/standard_options.t line 68.
#                   'Can't locate object method "make_PID_file" via package "Daemon" at /home/sveta/src/percona-toolkit/bin/pt-deadlock-logger line 4761.
# '
#     doesn't match '(?^:PID file /tmp/pt-deadlock-logger-test.pid.102629 already exists)'
not ok 3 - It lives daemonized

#   Failed test 'It lives daemonized'
#   at t/pt-deadlock-logger/standard_options.t line 88.
#                   ''
#     doesn't match '(?^:pt\-deadlock\-logger\ h\=127\.1\,P\=12345\,u\=msandbox\,p\=msandbox)'
# 
not ok 4 - PID file created

#   Failed test 'PID file created'
#   at t/pt-deadlock-logger/standard_options.t line 96.
# 
Cannot open /tmp/pt-deadlock-logger-test.pid.102629: No such file or directory at t/pt-deadlock-logger/standard_options.t line 101.
# Tests were run but no plan was declared and done_testing() was not seen.
# Looks like your test exited with 2 just after 4.
Dubious, test returned 2 (wstat 512, 0x200)
Failed 3/4 subtests