RA: pgsql: Several enhancements to by Keisuke MORI

1. In 'start', wait until the postmaster gets ready to answer by

checking as same as 'monitor' does. The maximum wait time to complete
to startup can be customized by an additional parameter 'start_wait'.

2. Add a cleanup code for 'postmaster.pid' when stop and before

starting.

3. In 'stop', wait until the postmaster completes to the fast mode

shutdown. The maximum wait time to complete to shutdown can be
customized by an additional parameter 'stop_wait'.

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extra : convert_revision : d24ab11e98116d43d9b1a18e0aafd469baca654a