wt-status: fix multiple small leaks

wt-status: fix multiple small leaks

rev.prune_data is populated (in multiple functions) via copy_pathspec,
and therefore needs to be cleared after running the diff in those
functions.

rev(_info).pending is populated indirectly via setup_revisions, and also
needs to be cleared once diffing is done.

These leaks were found while running t0008 or t0021. The rev.prune_data
leaks are small (80B) but noisy, hence I won't bother including their
logs - the rev.pending leaks are bigger, and can happen early in the
course of other commands, and therefore possibly more valuable to fix -
see example log from a rebase below:

Direct leak of 2048 byte(s) in 1 object(s) allocated from:
    #0 0x49ab79 in realloc ../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
    #1 0x9ac2a6 in xrealloc wrapper.c:126:8
    #2 0x83da03 in add_object_array_with_path object.c:337:3
    #3 0x8f5d8a in add_pending_object_with_path revision.c:329:2
    #4 0x8ea50b in add_pending_object_with_mode revision.c:336:2
    #5 0x8ea4fd in add_pending_object revision.c:342:2
    #6 0x8ea610 in add_head_to_pending revision.c:354:2
    #7 0x9b55f5 in has_uncommitted_changes wt-status.c:2474:2
    #8 0x9b58c4 in require_clean_work_tree wt-status.c:2553:6
    #9 0x606bcc in cmd_rebase builtin/rebase.c:1970:6
    #10 0x4cd91d in run_builtin git.c:467:11
    #11 0x4cb5f3 in handle_builtin git.c:719:3
    #12 0x4ccf47 in run_argv git.c:808:4
    #13 0x4caf49 in cmd_main git.c:939:19
    #14 0x69dc0e in main common-main.c:52:11
    #15 0x7f2d18909349 in __libc_start_main (/lib64/libc.so.6+0x24349)

Indirect leak of 5 byte(s) in 1 object(s) allocated from:
    #0 0x486834 in strdup ../projects/compiler-rt/lib/asan/asan_interceptors.cpp:452:3
    #1 0x9ac048 in xstrdup wrapper.c:29:14
    #2 0x83da8d in add_object_array_with_path object.c:349:17
    #3 0x8f5d8a in add_pending_object_with_path revision.c:329:2
    #4 0x8ea50b in add_pending_object_with_mode revision.c:336:2
    #5 0x8ea4fd in add_pending_object revision.c:342:2
    #6 0x8ea610 in add_head_to_pending revision.c:354:2
    #7 0x9b55f5 in has_uncommitted_changes wt-status.c:2474:2
    #8 0x9b58c4 in require_clean_work_tree wt-status.c:2553:6
    #9 0x606bcc in cmd_rebase builtin/rebase.c:1970:6
    #10 0x4cd91d in run_builtin git.c:467:11
    #11 0x4cb5f3 in handle_builtin git.c:719:3
    #12 0x4ccf47 in run_argv git.c:808:4
    #13 0x4caf49 in cmd_main git.c:939:19
    #14 0x69dc0e in main common-main.c:52:11
    #15 0x7f2d18909349 in __libc_start_main (/lib64/libc.so.6+0x24349)

SUMMARY: AddressSanitizer: 2053 byte(s) leaked in 2 allocation(s).

Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>