Plug mem leaks in contexts test

Plug mem leaks in contexts test

==2464== 80 (16 direct, 64 indirect) bytes in 1 blocks are definitely lost in loss record 515 of 547
==2464==    at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==2464==    by 0x4057094: g_malloc (gmem.c:134)
==2464==    by 0x406F2D6: g_slice_alloc (gslice.c:836)
==2464==    by 0x406F31B: g_slice_alloc0 (gslice.c:848)
==2464==    by 0x41385BB: g_type_create_instance (gtype.c:1867)
==2464==    by 0x411E72A: g_object_constructor (gobject.c:1482)
==2464==    by 0x411DE1D: g_object_newv (gobject.c:1266)
==2464==    by 0x411DB93: g_object_new (gobject.c:1178)
==2464==    by 0x4220D74: _g_local_file_new (glocalfile.c:310)
==2464==    by 0x422C897: g_local_vfs_get_file_for_path (glocalvfs.c:84)
==2464==    by 0x41CA91C: g_vfs_get_file_for_path (gvfs.c:94)
==2464==    by 0x418C1B6: g_file_new_for_path (gfile.c:5898)
==2464==    by 0x8049509: test1_thread (contexts.c:110)

==2464== 80 (16 direct, 64 indirect) bytes in 1 blocks are definitely lost in loss record 516 of 547
==2464==    at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==2464==    by 0x4057094: g_malloc (gmem.c:134)
==2464==    by 0x406F2D6: g_slice_alloc (gslice.c:836)
==2464==    by 0x406F31B: g_slice_alloc0 (gslice.c:848)
==2464==    by 0x41385BB: g_type_create_instance (gtype.c:1867)
==2464==    by 0x411E72A: g_object_constructor (gobject.c:1482)
==2464==    by 0x411DE1D: g_object_newv (gobject.c:1266)
==2464==    by 0x411DB93: g_object_new (gobject.c:1178)
==2464==    by 0x4220D74: _g_local_file_new (glocalfile.c:310)
==2464==    by 0x422C897: g_local_vfs_get_file_for_path (glocalvfs.c:84)
==2464==    by 0x41CA91C: g_vfs_get_file_for_path (gvfs.c:94)
==2464==    by 0x418C1B6: g_file_new_for_path (gfile.c:5898)
==2464==    by 0x804964D: test_context_independence (contexts.c:144)

Bug #628331.