Update git submodules

* Update pbr from branch 'master'
  to 1ca77814931463993b15fbbb13a26e027a485cd3
  - Merge "Tie recursion calls to Dist object, not module"
  - Tie recursion calls to Dist object, not module
    
    In change I1f2b4d34e587389f7e11b99d000e14477cf5091b, we attempted to
    resolve an issue whereby using PBR as a PEP-517 backend could result in
    recursion. We did this by setting 'dist.pbr' to 'None' but later
    discovered this introduced a regression that prevented us from writing
    the 'pbr.json' file into generated sdists. The fix for the regression,
    change I407ae88ab8de4b61f94034b3d79a2ca7f7d79d16, stopped setting
    'dist.pbr' to 'None' and instead set a global flag to indicate whether
    we had already been called or not. Unfortunately it seems this fix is
    also insufficent. As discussed in tox#2712 [1], tox v4 has implemented
    its own implementation of PEP-517 - 'pyproject-api' [2] - and unlike
    'build' this implementation optionally allows re-use of the backend
    process for multiple PEP-517 commands. tox's 'Pep517VirtualEnvFrontend'
    does just this. This means if we run multiple commands that require
    generation of a 'Distribution' object - say,
    'prepare_metadata_for_build_wheel' followed by 'build_sdist' - anything
    but the first step will not result in proper population of said
    'Distribution' objects.
    
    The solution to this issue is simple: per $subject, instead of setting
    our recursion-detection canary at the module level, set it at the
    Distribution level.
    
    [1] https://github.com/tox-dev/tox/issues/2712
    [2] github.com/tox-dev/pyproject-api/
    
    Change-Id: I67909d732a74550fbcd7c06a9e2f4ac88c063444
    Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

pbr

@@ -1 +1 @@
-Subproject commit 535254d5c8b9c0159017febafc882b58c873abe2
+Subproject commit 1ca77814931463993b15fbbb13a26e027a485cd3