Revert "Update waitcondition API to use signal RPC interface"

This reverts commit f2f2697c9d8f926869f93f34c0a6df0df7cba20a.

This and/or the previous commit are causing Metadata to return blank
after signals are processed.

Change-Id: I1c8b3f18e63d9c74b00b27fc32c5d5746faa8235
Partial-Bug: #1337772
Merge "Revert "Update waitcondition API to use signal RPC interface""