poll an app until is scales to the correct number of instances

[#84506394]

Signed-off-by: Matthew McNew <mmcnew@pivotal.io>
assert the app runner command polls the right appname when removing an app

Signed-off-by: Chelsea Troy <ctroy@pivotal.io>
remove reference to DockerAppExists method

Signed-off-by: Matthew McNew <mmcnew@pivotal.io>
pull polling into seperate command factory tests

Signed-off-by: Chelsea Troy <ctroy@pivotal.io>
rename buffers to outputBuffers in tests

Signed-off-by: Matthew McNew <mmcnew@pivotal.io>
assert that the command returns in tests

Signed-off-by: Chelsea Troy <ctroy@pivotal.io>
assert that test execute commands return

Signed-off-by: Matthew McNew <mmcnew@pivotal.io>
test logs with regex safe Say matcher from test_helpers

Signed-off-by: Chelsea Troy <ctroy@pivotal.io>
check for the appName before instances when scaling an app

Signed-off-by: Matthew McNew <mmcnew@pivotal.io>