[app-mgmt-test] Fix helper apps to not exit with an error

boot-start-srv would exit with an error after it tried to close handle
0. Fix it to not exit at all.
port-start-srv would exit with return code 1 for its normal exit. Fix it
to return 0.

Bug: 147698516
Change-Id: I24eba999b7139c1a1892dcd79b6a88d6c1cf85a2
2 files changed