mediainfo: post media-info before set caps on srcpad
mediainfo: post media-info before set caps on srcpad

Fix wav playing problem, media-info msg should be posting before
set caps on srcpad.

:Issues Addressed:
[MFTEVENTFT-8678]

Change-Id: I7d7d57454ccc7a0609c3ef1ed6ef57d82903ba70
Reviewed-on: https://gpro.lgsvl.com/66287
Reviewed-by: Wonchul Lee <9841bdbec9dbb2acc2dcaaa1dab0491399f0e464@lge.com>
Tested-by: Wonchul Lee <9841bdbec9dbb2acc2dcaaa1dab0491399f0e464@lge.com>

justinjoy/gst-plugins-cool,justinjoy/gst-plugins-cool