Camera2Client: avoid two consecutive sets of configure_streams calls

When mediaRecorder starts without an active preview stream, Camera2Client
starts preview then immediately start recording, which could cause the second
configure_streams to call into HAL before any preview request is sent. This
could cause HAL to run into bad state. This change work around this issue
by making sure the first preview request is submitted to the HAL before
start recording.

Bug: 17915062
Change-Id: I94ae64ee76487603695a469240da601ddcb29a66