Make waitTimeBeforeCheckStatus field customisable

### Context
Sometimes  we need to be able to customise the delay before verifying the remote server status

### Description
We made the existing field ```waitTimeBeforeCheckStatus``` be customisable from the pom.xml configuration or by using environment variables

### Example
```xml
<plugin>
  <groupId>com.agf.maven.mojo</groupId>
  <artifactId>maven-test-release-plugin</artifactId>
  <configuration>
    <serverMainClass>${serverMainClass}</serverMainClass>
    <server>
      <groupId>com.agf.sam</groupId>
      <artifactId>sam-server</artifactId>
      <classifier>assembly</classifier>
    </server>
     <localServerJvmArgs>-Xmx128m</localServerJvmArgs>
     <sleepAfterLocalStart>60</sleepAfterLocalStart>
     <waitTimeBeforeCheckStatus>10</waitTimeBeforeCheckStatus>
  </configuration>
</plugin>
```