use ISO 8601 time format in sweeper ls -l output

"sweeper ls -l" output did not contain year in the format
of creation and last access timestamps. This patchs modifies
ouptut to show time in ISO 8601 time format :

admin > sweeper ls -l
  0 000029A61FE585D94C74955AE61BF3AB396F  CACHED          993 2014-02-21T17:47:37 2014-02-21T17:47:37
  1 00009C6579BE112B40848D2F1221CB5D03FC  CACHED          993 2014-02-21T21:36:57 2014-02-21T21:36:57

RELEASE NOTES:

"sweeper ls -l" output did not contain year in the format
of creation and last access timestamps. This patchs modifies
ouptut to show time in ISO 8601 time format :

admin > sweeper ls -l
  0 000029A61FE585D94C74955AE61BF3AB396F  CACHED          993 2014-02-21T17:47:37 2014-02-21T17:47:37
  1 00009C6579BE112B40848D2F1221CB5D03FC  CACHED          993 2014-02-21T21:36:57 2014-02-21T21:36:57

Patch: http://rb.dcache.org/r/6634/
Require-notes: yes
Require-book: no
Acked-by: Tigran Mkrtchyan
Target: trunk