Wait till test receives preapproval request before committing

To prevent mixing up of broadcasts intended for CONFIRM_PRE_APPROVAL and
CONFIRM_INSTALL between the intended receivers, wait till we get the
preapproval broadcast before committing the session.

Bug: 289300824
FIXES: 297494812
Test: atest CtsPackageInstallTestCases:PreapprovalInstallTest
--iterations 100

Change-Id: Id894df683ba04fb00d3315c64638ce5d25d45bb7
(cherry picked from commit b3a1fe90bb1808735cbe6919a420e4a1cf1a0012)