src/pmcd/rc_pmcd: be more careful with auto-install/-remove
src/pmcd/rc_pmcd: be more careful with auto-install/-remove

Since _pmda_setup is run in the background, and this may cause
the "rc" script to be run again (sort of recursively), it is
important to avoid race conditions here.

aeg-aeg/pcpfans,wuliming/pcp,wuliming/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,aeg-aeg/pcpfans,aeg-aeg/pcpfans,adfernandes/pcp,wuliming/pcp,wuliming/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,aeg-aeg/pcpfans,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp