FYI, I had installed the agent prior to upgrading the OS to Yosemite, so it didn't require a new installation. After uninstalling the agent on my Yosemite system, I got the same error.
Evidently, Apple removed the StartupItemContext file in Yosemite. Our agent-upgrade script (and software from other vendors, apparantly) relied on that file. So, we will need to make changes to our installation script prior to providing full support for Yosemite.
I found one article that suggested manually creating that file on a Yosemite system. I did that and it "appears" that the agent installed and is functioning correctly. However, we cannot guarentee that everything will truly function correctly. So, this is experimental until we release a fully-supported build.
I manually created the StartupItemContext file, as shown below, then reran the bootstrap. You can check the syntax from a pre-Yosemite system to validate the contents.
*************************************
#!/bin/sh
unset LAUNCHD_SOCKET
exec launchctl bsexec / "$@"
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Also, the .tmp_inst directory path is /opt/altiris/notification/nsagent/.tmp_inst. This is removed after a successful installation of the agent, leaving just the install log files.
I suppose you could delete the StartupItemContext file after the agent is installed to keep the OS clean and original.