RFR(T): 8221527: [TESTBUG] DockerBasicTest.java contains hard-coded reference to JDK 10

[mikhailo.seledtsov at oracle.com]

Please review this simple/trivial change that removes hard-coded 
reference to JDK 10 in the image name,
and uses docker test library method instead.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8221527
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8221527.00/
     Testing:
        Ran the affected test

Thank you,
Misha