Remove org.apache.http.legacy from bootclasspath

Updates the tests to work when org.apache.http.legacy is no longer on the
bootclasspath.

1) Added new test to verify that the org.apache.http classes are visible
   to an APK that is targeted at an earlier release (27).

2) Modified CtsApacheHttpLegacyCurrentApiSignatureTestCases to verify
   that the org.apache.http classes are not visible to an APK that is
   targeted at the current release.

3) Added new test to verify that the org.apache.http classes are visible
   to an APK that is targeted at the current release which has a
   <uses-library android:name="org.apache.http.legacy"/> entry in its
   manifest.

Test: cts/tests/signature/runSignatureTests.sh
Bug: 18027885
Change-Id: I1aba8e4278a4e03f90b58e8e30eba9f3fecfe6f7
9 files changed