Checkmk Werk 15289: mk_oracle: Revert werk 15559, use tnsping when available

ID: 15289 Title: mk_oracle: Revert werk 15559, use tnsping when available Component: agents Level: 1 Class: Bug fix Version: 2.3.0b1 <a href="https://checkmk.com/werk/15559">Werk 15559</a> removed the invocation of <tt>tnsping</tt>. <tt>tnsping</tt> was used to check if the tns-alias could be reached. If it could not be reached via <tt>tnsping</tt>, hostname and port is used to connect to the database. With <a href="https://checkmk.com/werk/15559">Werk 15559</a> the invocation of <tt>tnsping</tt> was completely removed. tns-alias was always used. This lead to problems with different configurations of <tt>mk_oracle</tt>. This change introduces a check if the <tt>tnsping</tt> binary is available. If the binary is available, the logic of <tt>mk_oracle</tt> before Werk 15559 is restored. If the binary is not available, it is assumed that the tns-alias can be reached.