Buck: unsign all jgit jars

Change-Id: I25749b80f2060f3322844cd2b94075acd3874e51
(cherry picked from commit 0b579f89efe2e9889b84f5eb609a9afd422cca44)
Buck: fix api_install rule

Change-Id: I069b52004781b3b1a8d64514da3f2e4da8047816
(cherry picked from commit a3f72e4bb84deb1892e931d850e06f8ee8a55b95)
Merge "Buck: fix api_install rule" into stable-2.8