Fix perf_capture_realtime without a start_time
Fix perf_capture_realtime without a start_time

A number of specs test perf_capture_realtime without a start time and
without a last_perf_capture_on.  This leads to a comparison of nil and
Time failure.

d-m-u/manageiq,mzazrivec/manageiq,skateman/manageiq,skateman/manageiq,agrare/manageiq,djberg96/manageiq,ManageIQ/manageiq,chessbyte/manageiq,chessbyte/manageiq,kbrock/manageiq,gmcculloug/manageiq,hstastna/manageiq,ManageIQ/manageiq,jrafanie/manageiq,jrafanie/manageiq,billfitzgerald0120/manageiq,hstastna/manageiq,d-m-u/manageiq,jvlcek/manageiq,djberg96/manageiq,billfitzgerald0120/manageiq,pkomanek/manageiq,mzazrivec/manageiq,chessbyte/manageiq,chessbyte/manageiq,d-m-u/manageiq,NickLaMuro/manageiq,lpichler/manageiq,gmcculloug/manageiq,hstastna/manageiq,ManageIQ/manageiq,NickLaMuro/manageiq,kbrock/manageiq,pkomanek/manageiq,d-m-u/manageiq,agrare/manageiq,jvlcek/manageiq,hstastna/manageiq,jrafanie/manageiq,NickLaMuro/manageiq,lpichler/manageiq,billfitzgerald0120/manageiq,jvlcek/manageiq,jvlcek/manageiq,NickLaMuro/manageiq,djberg96/manageiq,kbrock/manageiq,ManageIQ/manageiq,lpichler/manageiq,jrafanie/manageiq,skateman/manageiq,agrare/manageiq,gmcculloug/manageiq,skateman/manageiq,pkomanek/manageiq,lpichler/manageiq,gmcculloug/manageiq,mzazrivec/manageiq,djberg96/manageiq,agrare/manageiq,mzazrivec/manageiq,billfitzgerald0120/manageiq,pkomanek/manageiq,kbrock/manageiq