Don't reinflate search bar when dialog is already showing

Change https://android-git.corp.google.com/g/27729 started reinflating
the entire search bar every time the search source was changed, to get
around problems with bad state in AutoCompleteTextView
(http://b/issue?id=2132686). This had some side-effects if the
search dialog was already visible, as it is when selecting a
source in "More results" or when presing the search key to go to
QSB from in-app search.

This change changes the reinflation to only happen if the dialog is
not already showing.

Fixes:

http://b/issue?id=2166640
"After selecting More results from suggestions, the search box is no longer visible."

http://b/issue?id=2166675
"Calling QSB with the hardware key does not place focus in the search tab."

http://b/issue?id=2166712
"back key has unexpected behaviour in QSB after selecting "More results" from suggestions."

Change-Id: I8d48149c3e9ad97ec11c49ec7efb356f27dfe4f6